CriticalCVE-2026-99284

    Linux Kernel: security vulnerability (CVE-2026-99284)

    Published Last modified Sources: CVE.org, pwn.watch

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    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: net: skbuff: propagate shared-frag marker in skb_zerocopy() skb_zerocopy() moves frag descriptors from @from into @to and takes a reference on each frag, but it does not copy skb_shinfo(from)->flags into skb_shinfo(to)->flags. A destination skb holding the same page-cache backed frags as the source therefore reports skb_has_shared_frag() as false.

    Update Linux Kernel to version 6.18.61, Linux Kernel to version 7.2.15, Linux Kernel to version 7.3.2.

    Affected
    • Linux Kernel lt 3.14..6.18.61
    • Linux Kernel lt 6.19..7.2.15
    • Linux Kernel lt 7.3..7.3.2
    • Linux Kernel lt 7.4..7.4-rc1
    Fixed in
    • Linux Kernel 6.18.61
    • Linux Kernel 7.2.15
    • Linux Kernel 7.3.2
    • Linux Kernel 7.4-rc1

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

    Metrics

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    Priority

    No value is available for this vulnerability.

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    CVSS v3

    No value is available for this vulnerability.

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    EPSS score

    No value is available for this vulnerability.

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    Severity
    Critical
    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
    30.00 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
    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
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    Published

    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
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    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

    In the Linux kernel, the following vulnerability has been resolved: net: skbuff: propagate shared-frag marker in skb_zerocopy() skb_zerocopy() moves frag descriptors from @from into @to and takes a reference on each frag, but it does not copy skb_shinfo(from)->flags into skb_shinfo(to)->flags. A destination skb holding the same page-cache backed frags as the source therefore reports skb_has_shared_frag() as false. That breaks the invariant relied on by later in-place writers. ESP input checks skb_has_shared_frag() before deciding whether an uncloned nonlinear skb can skip skb_cow_data(); with the marker lost, an skb that skb_zerocopy() built for nfnetlink_queue or for an openvswitch upcall is decrypted in place, letting an unprivileged user write into the page cache of a root-owned read-only file. Propagate SKBFL_SHARED_FRAG when frag descriptors are copied, as done for the other frag-transfer helpers.

    Source: cvelistv5, pwn.watch, 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
    LinuxLinux
    • 6.19 – < 7.2.15
    • 3.14 – < 6.18.61
    • 7.3 – < 7.3.2
    • 7.4 – < 7.4-rc1
    • 7.2.15
    • 6.18.61
    • 7.3.2
    • 7.4-rc1

    Vendors and products

    References & sources

    • git.kernel.orgstable/c/1a9c180cd8435917b7516edfb1c9148032c28773
    • git.kernel.orgstable/c/1c623e3cbf43f12dd4a72712079bfa247a9b8ba3
    • git.kernel.orgstable commit: propagate shared-frag marker in skb_zerocopy() (mainline)pwn-watch
    • git.kernel.orgstable/c/d7d6ff98d5d1b400f02211f962ac32cc0020aeab
    • pwn.watchpwn.watch: Linux kernel: unpatched ZDI bug reports with repro details leaked to public LKML (ksmbd RCE, CVSS 9.0)pwn-watch
    • CVE.org (MITRE)CVE-2026-99284: net: skbuff: propagate shared-frag marker in skb_zerocopy()pwn-watch
    • blog.cloudlinux.comZDI-CAN-33367: Linux Kernel Local Root Zero-Day, Mitigation for CloudLinuxpwn-watch
    • thehackernews.comTwo CVSS 9.0 Linux KSMBD RCE Flaws Disclosed on Public Mailing Lists Before Kernel Fixespwn-watch
    • phoronix.comSeveral Linux Kernel Vulnerabilities Accidentally Posted To Public Kernel Mailing Listpwn-watch
    • lore.kernel.orgZDI-CAN-33549: KSMBD SMB Direct integer underflow RCE (CVSS 9.0)pwn-watch
    • lore.kernel.orgZDI-CAN-33774: KSMBD protocol dispatch race RCE (CVSS 9.0)pwn-watch
    • lore.kernel.orgZDI-CAN-33367: skbuff skb_zerocopy local privilege escalation (CVSS 7.8)pwn-watch
    • lore.kernel.orgZDI-CAN-34068: vmwgfx dirty tracking out-of-bounds write LPE (Greg KH reply)pwn-watch
    • lore.kernel.orgZDI-CAN-34076: nvmet Get Log Page uninitialized resource info disclosure (Greg KH reply)pwn-watch
    • git.kernel.orgksmbd: wait for negotiation before receiving another PDU (fix for the ksmbd race)pwn-watch
    • almalinux.orgZDI-CAN-33367: Patched kernels available in testingpwn-watch

    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. ReceivedLinux

      Description added or changed

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      In the Linux kernel, the following vulnerability has been resolved: net: skbuff: propagate shared-frag marker in skb_zerocopy() skb_zerocopy() moves frag descriptors from @from into @to and takes a reference on each frag, but it does not copy skb_shinfo(from)->flags into skb_shinfo(to)->flags. A destination skb holding the same page-cache backed frags as the source therefore reports skb_has_shared_frag() as false. That breaks the invariant relied on by later in-place writers. ESP input checks skb_has_shared_frag() before deciding whether an uncloned nonlinear skb can skip skb_cow_data(); with the marker lost, an skb that skb_zerocopy() built for nfnetlink_queue or for an openvswitch upcall is decrypted in place, letting an unprivileged user write into the page cache of a root-owned read-only file. Propagate SKBFL_SHARED_FRAG when frag descriptors are copied, as done for the other frag-transfer helpers.
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99284.json">CVE-2026-99284</a>
      Referenceadded
      —
      https://git.kernel.org/stable/c/1a9c180cd8435917b7516edfb1c9148032c28773
      Referenceadded
      —
      https://git.kernel.org/stable/c/1c623e3cbf43f12dd4a72712079bfa247a9b8ba3
      Referenceadded
      —
      https://git.kernel.org/stable/c/79dc34beb1fdb3da79753e51e15c68591a2561fe
      Referenceadded
      —
      https://git.kernel.org/stable/c/d7d6ff98d5d1b400f02211f962ac32cc0020aeab

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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