MediumCVE-2023-25136

    OpenBSD OpenSSH: Double Free (CVE-2023-25136)

    Published Last modified Sources: Siemens ProductCERT, CVE.org

    What is affected, what to do

    OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. This is fixed in OpenSSH 9.2.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Affected
    • OpenBSD OpenSSH eq 9.1..9.1
    • Fedora eq 37..37
    • Fedora eq 38..38

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

    Metrics

    6.5

    Priority

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

    Source: NVD, CVSS v3

    6.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: Siemens ProductCERT, CVE.org

    89.8 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.79

    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
    114.28 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
    no public PoC known
    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
    6.5 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
    6.5
    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
    89.8 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    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
    99.79
    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: proof of concept · not automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 27 February 2024
    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-415

    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

    OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. This is fixed in OpenSSH 9.2. The double free can be leveraged, by an unauthenticated remote attacker in the default configuration, to jump to any location in the sshd address space. One third-party report states "remote code execution is theoretically possible."

    Source: siemens_advisory, 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
    netappontap_select_deploy_administration_utility
    • —
    • —
    openbsdopenssh
    • 9.1
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Othernetapp500f_firmware—
    Othernetappa250_firmware—
    Othernetappc250_firmware—
    Otherfedoraprojectfedora37
    Otherfedoraprojectfedora38

    Weakness classes (CWE)

    References & sources

    • ftp.openbsd.orgpub/OpenBSD/patches/7.2/common/017_sshd.patch.sig
    • openwall.comlists/oss-security/2023/02/02/2
    • bugzilla.mindrot.orgshow_bug.cgi?id=3522
    • github.comopenssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24…
    • jfrog.comblog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-pr…
    • news.ycombinator.comitem?id=34711565
    • openwall.com[oss-security] 20230213 Re: double-free vulnerability in OpenSSH server 9.1 (CVE-2023-25136)Mailing list
    • openwall.com[oss-security] 20230222 Re: double-free vulnerability in OpenSSH server 9.1 (CVE-2023-25136)Mailing list
    • openwall.com[oss-security] 20230222 Re: Re: double-free vulnerability in OpenSSH server 9.1 (CVE-2023-25136)Mailing list
    • openwall.com[oss-security] 20230223 Re: Re: double-free vulnerability in OpenSSH server 9.1 (CVE-2023-25136)Mailing list
    • openwall.com[oss-security] 20230306 Re: Re: double-free vulnerability in OpenSSH server 9.1 (CVE-2023-25136)Mailing list
    • openwall.com[oss-security] 20230309 Re: Re: double-free vulnerability in OpenSSH server 9.1 (CVE-2023-25136)Mailing list
    • security.netapp.comadvisory/ntap-20230309-0003
    • lists.fedoraproject.orgFEDORA-2023-1176c8b10cVendor advisory
    • lists.fedoraproject.orgFEDORA-2023-123647648eVendor advisory
    • security.gentoo.orgGLSA-202307-01Vendor advisory
    • 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 modifiedMITRE

      Show 46 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/13/1
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/22/1
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/22/2
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/23/3
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/03/06/1
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/03/09/2
      Referenceadded
      —
      https://bugzilla.mindrot.org/show_bug.cgi?id=3522
      Referenceadded
      —
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/017_sshd.patch.sig
      Referenceadded
      —
      https://github.com/openssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24138ec3946
      Referenceadded
      —
      https://jfrog.com/blog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-proof-of-concept/
      Referenceadded
      —
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JGAUIXJ3TEKCRKVWFQ6GDAGQFTIIGQQP/
      Referenceadded
      —
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R7LKQDFZWKYHQ65TBSH2X2HJQ4V2THS3/
      Referenceadded
      —
      https://news.ycombinator.com/item?id=34711565
      Referenceadded
      —
      https://security.gentoo.org/glsa/202307-01
      Referenceadded
      —
      https://security.netapp.com/advisory/ntap-20230309-0003/
      Referenceadded
      —
      https://www.openwall.com/lists/oss-security/2023/02/02/2
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/13/1
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/1
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/2
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/23/3
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/03/06/1
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/03/09/2
      —
      Referenceremoved
      https://bugzilla.mindrot.org/show_bug.cgi?id=3522
      —
      Referenceremoved
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/017_sshd.patch.sig
      —
      Referenceremoved
      https://github.com/openssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24138ec3946
      —
      Referenceremoved
      https://jfrog.com/blog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-proof-of-concept/
      —
      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JGAUIXJ3TEKCRKVWFQ6GDAGQFTIIGQQP/
      —
      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R7LKQDFZWKYHQ65TBSH2X2HJQ4V2THS3/
      —
      Referenceremoved
      https://news.ycombinator.com/item?id=34711565
      —
      Referenceremoved
      https://security.gentoo.org/glsa/202307-01
      —
      Referenceremoved
      https://security.netapp.com/advisory/ntap-20230309-0003/
      —
      Referenceremoved
      https://www.openwall.com/lists/oss-security/2023/02/02/2
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/13/1 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/1 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/2 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/23/3 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/03/06/1 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/03/09/2 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      https://bugzilla.mindrot.org/show_bug.cgi?id=3522 Types: Exploit, Issue Tracking, Third Party Advisory
      —
      Reference typeremoved
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/017_sshd.patch.sig Types: Patch, Vendor Advisory
      —
      Reference typeremoved
      https://github.com/openssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24138ec3946 Types: Patch, Third Party Advisory
      —
      Reference typeremoved
      https://jfrog.com/blog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-proof-of-concept/ Types: Exploit, Third Party Advisory
      —
      Reference typeremoved
      https://news.ycombinator.com/item?id=34711565 Types: Issue Tracking, Third Party Advisory
      —
      Reference typeremoved
      https://security.gentoo.org/glsa/202307-01 Types: Third Party Advisory
      —
      Reference typeremoved
      https://security.netapp.com/advisory/ntap-20230309-0003/ Types: Third Party Advisory
      —
      Reference typeremoved
      https://www.openwall.com/lists/oss-security/2023/02/02/2 Types: Exploit, Mailing List, Third Party Advisory
      —

      Source identifier: cve@mitre.org

    2. Record modifiedCVE Program

      Show 46 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/13/1
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/22/1
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/22/2
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/02/23/3
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/03/06/1
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2023/03/09/2
      Referenceadded
      —
      https://bugzilla.mindrot.org/show_bug.cgi?id=3522
      Referenceadded
      —
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/017_sshd.patch.sig
      Referenceadded
      —
      https://github.com/openssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24138ec3946
      Referenceadded
      —
      https://jfrog.com/blog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-proof-of-concept/
      Referenceadded
      —
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JGAUIXJ3TEKCRKVWFQ6GDAGQFTIIGQQP/
      Referenceadded
      —
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R7LKQDFZWKYHQ65TBSH2X2HJQ4V2THS3/
      Referenceadded
      —
      https://news.ycombinator.com/item?id=34711565
      Referenceadded
      —
      https://security.gentoo.org/glsa/202307-01
      Referenceadded
      —
      https://security.netapp.com/advisory/ntap-20230309-0003/
      Referenceadded
      —
      https://www.openwall.com/lists/oss-security/2023/02/02/2
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/13/1
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/1
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/2
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/02/23/3
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/03/06/1
      —
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2023/03/09/2
      —
      Referenceremoved
      https://bugzilla.mindrot.org/show_bug.cgi?id=3522
      —
      Referenceremoved
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/017_sshd.patch.sig
      —
      Referenceremoved
      https://github.com/openssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24138ec3946
      —
      Referenceremoved
      https://jfrog.com/blog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-proof-of-concept/
      —
      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JGAUIXJ3TEKCRKVWFQ6GDAGQFTIIGQQP/
      —
      Referenceremoved
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R7LKQDFZWKYHQ65TBSH2X2HJQ4V2THS3/
      —
      Referenceremoved
      https://news.ycombinator.com/item?id=34711565
      —
      Referenceremoved
      https://security.gentoo.org/glsa/202307-01
      —
      Referenceremoved
      https://security.netapp.com/advisory/ntap-20230309-0003/
      —
      Referenceremoved
      https://www.openwall.com/lists/oss-security/2023/02/02/2
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/13/1 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/1 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/22/2 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/02/23/3 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/03/06/1 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2023/03/09/2 Types: Mailing List, Third Party Advisory
      —
      Reference typeremoved
      https://bugzilla.mindrot.org/show_bug.cgi?id=3522 Types: Exploit, Issue Tracking, Third Party Advisory
      —
      Reference typeremoved
      https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/017_sshd.patch.sig Types: Patch, Vendor Advisory
      —
      Reference typeremoved
      https://github.com/openssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24138ec3946 Types: Patch, Third Party Advisory
      —
      Reference typeremoved
      https://jfrog.com/blog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-proof-of-concept/ Types: Exploit, Third Party Advisory
      —
      Reference typeremoved
      https://news.ycombinator.com/item?id=34711565 Types: Issue Tracking, Third Party Advisory
      —
      Reference typeremoved
      https://security.gentoo.org/glsa/202307-01 Types: Third Party Advisory
      —
      Reference typeremoved
      https://security.netapp.com/advisory/ntap-20230309-0003/ Types: Third Party Advisory
      —
      Reference typeremoved
      https://www.openwall.com/lists/oss-security/2023/02/02/2 Types: Exploit, Mailing List, Third Party Advisory
      —

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

    3. Record modifiedSiemens ADP

      Show 2 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/2023/25xxx/CVE-2023-25136.json">CVE-2023-25136</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-398330.html

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

    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2023-25136
    <a href="https://intel.neosec.eu/en/cve/CVE-2023-25136"><img src="https://intel.neosec.eu/badge/cve/CVE-2023-25136.svg?lang=en" alt="CVE-2023-25136 – NEOSEC Intel" height="20"></a>