MediumCVE-2021-33910

    Systemd: security vulnerability (CVE-2021-33910)

    Published Last modified Sources: Debian, CVE.org

    What is affected, what to do

    basic/unit-name.c in systemd prior to 246.15, 247.8, 248.5, and 249.1 has a Memory Allocation with an Excessive Size Value (involving strdupa and alloca for a pathname controlled by a local attacker) that results in an operating system crash.

    An exploit is publicly available. Update Systemd to version 246.15, Systemd to version 247.8, Systemd to version 248.5.

    Affected
    • Systemd lt *..246.15
    • Systemd lt 247..247.8
    • Systemd lt 248..248.5
    • Systemd lt 249..249.1
    • Fedora eq 33..33
    • Fedora eq 34..34
    • Debian Linux eq 10.0..10.0
    Fixed in
    • Systemd 246.15
    • Systemd 247.8
    • Systemd 248.5
    • Systemd 249.1

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    5.5

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    5.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: Debian, CVE.org

    8.8 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 95.2

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    99.94 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    PoC (publicly reported)
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    5.5 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    5.5
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    8.8 %
    Moderate — model estimates 1-10% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    95.2
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 9 June 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-770

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    basic/unit-name.c in systemd prior to 246.15, 247.8, 248.5, and 249.1 has a Memory Allocation with an Excessive Size Value (involving strdupa and alloca for a pathname controlled by a local attacker) that results in an operating system crash.

    Source: Debian Security Advisories, cvelistv5, NVD (NIST)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    netapphci_management_node
    • —
    • —
    netappsolidfire
    • —
    • —
    systemd_projectsystemd
    • < 246.15
    • 247 – < 247.8
    • 249 – < 249.1
    • 248 – < 248.5
    • 246.15
    • 247.8
    • 249.1
    • 248.5

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebiandebian_linux10.0
    Linuxdebiansystemdbuster
    Otherfedoraprojectfedora33
    Otherfedoraprojectfedora34

    Weakness classes (CWE)

    • CWE-770Allocation of Resources Without Limits or Throttling

      Base

      The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

      Entry at MITRE CWE-770

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    Packet StormSequoia A Deep Root In Linuxs Filesystem Layer (opens in a new tab)packetstormsecurity.comPoC (publicly reported)reported, not verified—

    References & sources

    • github.comsystemd/systemd/pull/20256/commits/441e0115646d54f080e5c3bb0ba4…x_refsource_MISC
    • openwall.comlists/oss-security/2021/07/20/2x_refsource_MISC
    • security.gentoo.orgGLSA-202107-48Vendor advisory, x_refsource_GENTOO
    • debian.orgDSA-4942Vendor advisory, x_refsource_DEBIAN
    • packetstormsecurity.comfiles/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.htmlx_refsource_MISC
    • github.comsystemd/systemd/commit/b34a4f0e6729de292cb3b0c03c1d48f246ad896bx_refsource_MISC
    • github.comsystemd/systemd-stable/commit/cfd14c65374027b34dbbc4f0551456c5d…x_refsource_MISC
    • github.comsystemd/systemd-stable/commit/b00674347337b7531c92fdb65590ab253…x_refsource_MISC
    • github.comsystemd/systemd-stable/commit/4a1c5f34bd3e1daed4490e9d97918e504…x_refsource_MISC
    • github.comsystemd/systemd-stable/commit/764b74113e36ac5219a4b82a05f311b5a…x_refsource_MISC
    • lists.fedoraproject.orgFEDORA-2021-2a6ba64260Vendor advisory, x_refsource_FEDORA
    • lists.fedoraproject.orgFEDORA-2021-166e461c8dVendor advisory, x_refsource_FEDORA
    • openwall.com[oss-security] 20210804 Re: Pop!_OS Membership to linux-distros listMailing list, x_refsource_MLIST
    • openwall.com[oss-security] 20210817 Re: Pop!_OS Membership to linux-distros listMailing list, x_refsource_MLIST
    • openwall.com[oss-security] 20210907 Re: Pop!_OS Membership to linux-distros listMailing list, x_refsource_MLIST
    • security.netapp.comadvisory/ntap-20211104-0008x_refsource_CONFIRM
    • Siemens ProductCERTproductcert/pdf/ssa-222547.pdfx_refsource_CONFIRM
    • Siemens ProductCERTproductcert/html/ssa-222547.html
    • Siemens ProductCERTproductcert/html/ssa-398330.html

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedSiemens ADP

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2021/33xxx/CVE-2021-33910.json">CVE-2021-33910</a>
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-222547.html
      Referenceadded
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      https://cert-portal.siemens.com/productcert/html/ssa-398330.html

      Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

    2. Record modifiedMITRE

      Show 48 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html
      Referenceadded
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      http://www.openwall.com/lists/oss-security/2021/08/04/2
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      http://www.openwall.com/lists/oss-security/2021/08/17/3
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      http://www.openwall.com/lists/oss-security/2021/09/07/3
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      https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
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      https://github.com/systemd/systemd-stable/commit/4a1c5f34bd3e1daed4490e9d97918e504d19733b
      Referenceadded
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      https://github.com/systemd/systemd-stable/commit/764b74113e36ac5219a4b82a05f311b5a92136ce
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      https://github.com/systemd/systemd-stable/commit/b00674347337b7531c92fdb65590ab253bb57538
      Referenceadded
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      https://github.com/systemd/systemd-stable/commit/cfd14c65374027b34dbbc4f0551456c5dc2d1f61
      Referenceadded
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      https://github.com/systemd/systemd/commit/b34a4f0e6729de292cb3b0c03c1d48f246ad896b
      Referenceadded
      —
      https://github.com/systemd/systemd/pull/20256/commits/441e0115646d54f080e5c3bb0ba477c892861ab9
      Referenceadded
      —
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2LSDMHAKI4LGFOCSPXNVVSEWQFAVFWR7/
      Referenceadded
      —
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/42TMJVNYRY65B4QCJICBYOEIVZV3KUYI/
      Referenceadded
      —
      https://security.gentoo.org/glsa/202107-48
      Referenceadded
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      https://security.netapp.com/advisory/ntap-20211104-0008/
      Referenceadded
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      https://www.debian.org/security/2021/dsa-4942
      Referenceadded
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      https://www.openwall.com/lists/oss-security/2021/07/20/2
      Referenceremoved
      http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html
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      Referenceremoved
      http://www.openwall.com/lists/oss-security/2021/08/04/2
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      http://www.openwall.com/lists/oss-security/2021/08/17/3
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      http://www.openwall.com/lists/oss-security/2021/09/07/3
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      https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
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      https://github.com/systemd/systemd-stable/commit/4a1c5f34bd3e1daed4490e9d97918e504d19733b
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      https://github.com/systemd/systemd-stable/commit/764b74113e36ac5219a4b82a05f311b5a92136ce
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      https://github.com/systemd/systemd-stable/commit/b00674347337b7531c92fdb65590ab253bb57538
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      https://github.com/systemd/systemd-stable/commit/cfd14c65374027b34dbbc4f0551456c5dc2d1f61
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      https://github.com/systemd/systemd/commit/b34a4f0e6729de292cb3b0c03c1d48f246ad896b
      —
      Referenceremoved
      https://github.com/systemd/systemd/pull/20256/commits/441e0115646d54f080e5c3bb0ba477c892861ab9
      —
      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2LSDMHAKI4LGFOCSPXNVVSEWQFAVFWR7/
      —
      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/42TMJVNYRY65B4QCJICBYOEIVZV3KUYI/
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      Referenceremoved
      https://security.gentoo.org/glsa/202107-48
      —
      Referenceremoved
      https://security.netapp.com/advisory/ntap-20211104-0008/
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      https://www.debian.org/security/2021/dsa-4942
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      Referenceremoved
      https://www.openwall.com/lists/oss-security/2021/07/20/2
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      Reference typeremoved
      http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html Types: Exploit, Third Party Advisory, VDB Entry
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2021/08/04/2 Types: Mailing List, Patch, Third Party Advisory
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      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2021/08/17/3 Types: Mailing List, Patch, Third Party Advisory
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      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2021/09/07/3 Types: Mailing List, Patch, Third Party Advisory
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      https://github.com/systemd/systemd-stable/commit/4a1c5f34bd3e1daed4490e9d97918e504d19733b Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd-stable/commit/764b74113e36ac5219a4b82a05f311b5a92136ce Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd-stable/commit/b00674347337b7531c92fdb65590ab253bb57538 Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd-stable/commit/cfd14c65374027b34dbbc4f0551456c5dc2d1f61 Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd/commit/b34a4f0e6729de292cb3b0c03c1d48f246ad896b Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd/pull/20256/commits/441e0115646d54f080e5c3bb0ba477c892861ab9 Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://security.gentoo.org/glsa/202107-48 Types: Third Party Advisory
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      Reference typeremoved
      https://security.netapp.com/advisory/ntap-20211104-0008/ Types: Third Party Advisory
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      Reference typeremoved
      https://www.debian.org/security/2021/dsa-4942 Types: Third Party Advisory
      —
      Reference typeremoved
      https://www.openwall.com/lists/oss-security/2021/07/20/2 Types: Exploit, Mailing List, Third Party Advisory
      —

      Source identifier: cve@mitre.org

    3. Record modifiedCVE Program

      Show 48 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html
      Referenceadded
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      http://www.openwall.com/lists/oss-security/2021/08/04/2
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      http://www.openwall.com/lists/oss-security/2021/08/17/3
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      http://www.openwall.com/lists/oss-security/2021/09/07/3
      Referenceadded
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      https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
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      https://github.com/systemd/systemd-stable/commit/4a1c5f34bd3e1daed4490e9d97918e504d19733b
      Referenceadded
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      https://github.com/systemd/systemd-stable/commit/764b74113e36ac5219a4b82a05f311b5a92136ce
      Referenceadded
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      https://github.com/systemd/systemd-stable/commit/b00674347337b7531c92fdb65590ab253bb57538
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      https://github.com/systemd/systemd-stable/commit/cfd14c65374027b34dbbc4f0551456c5dc2d1f61
      Referenceadded
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      https://github.com/systemd/systemd/commit/b34a4f0e6729de292cb3b0c03c1d48f246ad896b
      Referenceadded
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      https://github.com/systemd/systemd/pull/20256/commits/441e0115646d54f080e5c3bb0ba477c892861ab9
      Referenceadded
      —
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2LSDMHAKI4LGFOCSPXNVVSEWQFAVFWR7/
      Referenceadded
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      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/42TMJVNYRY65B4QCJICBYOEIVZV3KUYI/
      Referenceadded
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      https://security.gentoo.org/glsa/202107-48
      Referenceadded
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      https://security.netapp.com/advisory/ntap-20211104-0008/
      Referenceadded
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      https://www.debian.org/security/2021/dsa-4942
      Referenceadded
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      https://www.openwall.com/lists/oss-security/2021/07/20/2
      Referenceremoved
      http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html
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      Referenceremoved
      http://www.openwall.com/lists/oss-security/2021/08/04/2
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      http://www.openwall.com/lists/oss-security/2021/08/17/3
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      http://www.openwall.com/lists/oss-security/2021/09/07/3
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      https://cert-portal.siemens.com/productcert/pdf/ssa-222547.pdf
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      https://github.com/systemd/systemd-stable/commit/4a1c5f34bd3e1daed4490e9d97918e504d19733b
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      https://github.com/systemd/systemd-stable/commit/764b74113e36ac5219a4b82a05f311b5a92136ce
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      https://github.com/systemd/systemd-stable/commit/b00674347337b7531c92fdb65590ab253bb57538
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      https://github.com/systemd/systemd-stable/commit/cfd14c65374027b34dbbc4f0551456c5dc2d1f61
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      Referenceremoved
      https://github.com/systemd/systemd/commit/b34a4f0e6729de292cb3b0c03c1d48f246ad896b
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      Referenceremoved
      https://github.com/systemd/systemd/pull/20256/commits/441e0115646d54f080e5c3bb0ba477c892861ab9
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      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2LSDMHAKI4LGFOCSPXNVVSEWQFAVFWR7/
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      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/42TMJVNYRY65B4QCJICBYOEIVZV3KUYI/
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      Referenceremoved
      https://security.gentoo.org/glsa/202107-48
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      Referenceremoved
      https://security.netapp.com/advisory/ntap-20211104-0008/
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      Referenceremoved
      https://www.debian.org/security/2021/dsa-4942
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      Referenceremoved
      https://www.openwall.com/lists/oss-security/2021/07/20/2
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      Reference typeremoved
      http://packetstormsecurity.com/files/163621/Sequoia-A-Deep-Root-In-Linuxs-Filesystem-Layer.html Types: Exploit, Third Party Advisory, VDB Entry
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      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2021/08/04/2 Types: Mailing List, Patch, Third Party Advisory
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      http://www.openwall.com/lists/oss-security/2021/08/17/3 Types: Mailing List, Patch, Third Party Advisory
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      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2021/09/07/3 Types: Mailing List, Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd-stable/commit/4a1c5f34bd3e1daed4490e9d97918e504d19733b Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd-stable/commit/764b74113e36ac5219a4b82a05f311b5a92136ce Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd-stable/commit/b00674347337b7531c92fdb65590ab253bb57538 Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd-stable/commit/cfd14c65374027b34dbbc4f0551456c5dc2d1f61 Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd/commit/b34a4f0e6729de292cb3b0c03c1d48f246ad896b Types: Patch, Third Party Advisory
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      Reference typeremoved
      https://github.com/systemd/systemd/pull/20256/commits/441e0115646d54f080e5c3bb0ba477c892861ab9 Types: Patch, Third Party Advisory
      —
      Reference typeremoved
      https://security.gentoo.org/glsa/202107-48 Types: Third Party Advisory
      —
      Reference typeremoved
      https://security.netapp.com/advisory/ntap-20211104-0008/ Types: Third Party Advisory
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      Reference typeremoved
      https://www.debian.org/security/2021/dsa-4942 Types: Third Party Advisory
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      Reference typeremoved
      https://www.openwall.com/lists/oss-security/2021/07/20/2 Types: Exploit, Mailing List, Third Party Advisory
      —

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

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