HighCVE-2026-52943

    Linux Kernel: Use-After-Free (CVE-2026-52943)

    Published Last modified Sources: Siemens ProductCERT, Debian LTS, SUSE, Ubuntu, BSI, CVE.org, Msrc Update Guide

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: net: skbuff: fix missing zerocopy reference in pskb_carve helpers pskb_carve_inside_header() and pskb_carve_inside_nonlinear() both copy the old skb_shared_info header into a new buffer via memcpy(), which includes the destructor_arg pointer (uarg) for MSG_ZEROCOPY skbs. Neither function calls net_zcopy_get() for the new shinfo, creating an unaccounted holder: every skb_shared_info with destructor_arg set will call skb_zcopy_clear() once when freed, but the corresponding net_zcopy_get() was never called for the new copy.

    An exploit is publicly available. Update Linux Kernel to version 5.10.259, Linux Kernel to version 5.15.210, Linux Kernel to version 6.1.176.

    Affected
    • Linux Kernel lt 4.7..5.10.259
    • Linux Kernel lt 5.11..5.15.210
    • Linux Kernel lt 5.16..6.1.176
    • Linux Kernel lt 6.2..6.6.143
    • Linux Kernel lt 6.7..6.12.93
    • Linux Kernel lt 6.13..6.18.35
    • Linux Kernel lt 6.19..7.0.12
    Fixed in
    • Linux Kernel 5.10.259
    • Linux Kernel 5.15.210
    • Linux Kernel 6.1.176
    • Linux Kernel 6.6.143
    • Linux Kernel 6.12.93
    • Linux Kernel 6.18.35
    • Linux Kernel 7.0.12
    • Linux Kernel 7.1

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

    Metrics

    7.8

    Priority

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

    Source: NVD, CVSS v3

    7.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: Siemens ProductCERT, Debian LTS, SUSE, Ubuntu, BSI, CVE.org, Msrc Update Guide

    0.3 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 22.9

    Show all metrics
    Severity
    High
    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
    62.66 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
    7.8 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
    7.8
    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
    0.3 %
    Low — model estimates < 1% 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
    22.9
    Elevated — this CVE ranks above at least 10% of all CVEs scored today.
    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: total
    Source: CISA Vulnrichment, as of 16 October 2026
    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-416

    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: fix missing zerocopy reference in pskb_carve helpers pskb_carve_inside_header() and pskb_carve_inside_nonlinear() both copy the old skb_shared_info header into a new buffer via memcpy(), which includes the destructor_arg pointer (uarg) for MSG_ZEROCOPY skbs. Neither function calls net_zcopy_get() for the new shinfo, creating an unaccounted holder: every skb_shared_info with destructor_arg set will call skb_zcopy_clear() once when freed, but the corresponding net_zcopy_get() was never called for the new copy. Repeated calls drive uarg->refcnt to zero prematurely, freeing ubuf_info_msgzc while TX skbs still hold live destructor_arg pointers. KASAN reports use-after-free on a freed ubuf_info_msgzc: BUG: KASAN: slab-use-after-free in skb_release_data+0x77b/0x810 Read of size 8 at addr ffff88801574d3e8 by task poc/220 Call Trace: skb_release_data+0x77b/0x810 kfree_skb_list_reason+0x13e/0x610 skb_release_data+0x4cd/0x810 sk_skb_reason_drop+0xf3/0x340 skb_queue_purge_reason+0x282/0x440 rds_tcp_inc_free+0x1e/0x30 rds_recvmsg+0x354/0x1780 __sys_recvmsg+0xdf/0x180 Allocated by task 219: msg_zerocopy_realloc+0x157/0x7b0 tcp_sendmsg_locked+0x2892/0x3ba0 Freed by task 219: ip_recv_error+0x74a/0xb10 tcp_recvmsg+0x475/0x530 The skb consuming the late access still referenced the same uarg via shinfo->destructor_arg copied by pskb_carve_inside_nonlinear() without a refcount bump. This has been verified to be reliably exploitable: a working proof-of-concept achieves full root privilege escalation from an unprivileged local user on a default kernel configuration. The fix follows the pattern of pskb_expand_head() which has the same memcpy/cloned structure. For pskb_carve_inside_header(), net_zcopy_get() is placed after skb_orphan_frags() succeeds, so the orphan error path needs no cleanup. For pskb_carve_inside_nonlinear(), net_zcopy_get() is placed after all failure points and just before skb_release_data(), so no error path needs cleanup at all -- matching pskb_expand_head() more closely and avoiding the need for a balancing net_zcopy_put().

    Source: siemens_advisory, Debian LTS Advisories, suse_csaf, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, NVD (NIST), Microsoft Security Update Guide, CVE.org (MITRE), cvelistv5

    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
    • 6.13 – < 6.18.35
    • 6.7 – < 6.12.93
    • 5.11 – < 5.15.210
    • 6.19 – < 7.0.12
    • —
    • 4.7 – < 5.10.259
    • 5.16 – < 6.1.176
    • 6.2 – < 6.6.143
    • 6.18.35
    • 6.12.93
    • 5.15.210
    • 7.0.12
    • 7.1
    • 5.10.259
    • 6.1.176
    • 6.6.143
    Open SourceLinux Kernel
    • < 7.1
    • < 6.6.143
    • < 7.0.12
    • < 5.15.210
    • < 5.10.259
    • < 6.18.35
    • < 6.1.176
    • < 6.12.93
    • 7.1
    • 6.6.143
    • 7.0.12
    • 5.15.210
    • 5.10.259
    • 6.18.35
    • 6.1.176
    • 6.12.93
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel7.1
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-416Use After Free

      Variant

      The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

      Entry at MITRE CWE-416

    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
    PoC-in-GitHub (nomi-sec)CVE-2026-52943 (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    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 modifiedCISA ADP

      Weakness type: CWE-416

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-416

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    2. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-52943","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:23:07.278069Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    3. Record modifiedSiemens ADP

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/52xxx/CVE-2026-52943.json">CVE-2026-52943</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

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

    4. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/2e0e74c59b2761a414d9f48d7bee1e45220b2427
      Referenceadded
      —
      https://git.kernel.org/stable/c/474d6c771d798bca84f0a140b611e36743511e18
      Referenceadded
      —
      https://git.kernel.org/stable/c/8dbed691e43a50903658130bde0fcb5abc425b37
      Referenceadded
      —
      https://git.kernel.org/stable/c/96a4713ae041cc85e712bac682cd2e644004d6c6
      Referenceadded
      —
      https://git.kernel.org/stable/c/98d0912e9f841e5529a5b89a972805f34cb1c69d
      Referenceadded
      —
      https://git.kernel.org/stable/c/9b40bdc2a3298225dffab8158208a0d8c6300578
      Referenceadded
      —
      https://git.kernel.org/stable/c/ceafb893b12f23331dcc5ff9587e643c3a40ee9f
      Referenceadded
      —
      https://git.kernel.org/stable/c/fd470f0a97b8e9a125f520265d2f3b088ffb5b8a
      Referenceremoved
      https://git.kernel.org/stable/c/2e0e74c59b2761a414d9f48d7bee1e45220b2427
      —
      Referenceremoved
      https://git.kernel.org/stable/c/474d6c771d798bca84f0a140b611e36743511e18
      —
      Referenceremoved
      https://git.kernel.org/stable/c/8dbed691e43a50903658130bde0fcb5abc425b37
      —
      Referenceremoved
      https://git.kernel.org/stable/c/96a4713ae041cc85e712bac682cd2e644004d6c6
      —
      Referenceremoved
      https://git.kernel.org/stable/c/98d0912e9f841e5529a5b89a972805f34cb1c69d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/9b40bdc2a3298225dffab8158208a0d8c6300578
      —
      Referenceremoved
      https://git.kernel.org/stable/c/ceafb893b12f23331dcc5ff9587e643c3a40ee9f
      —
      Referenceremoved
      https://git.kernel.org/stable/c/fd470f0a97b8e9a125f520265d2f3b088ffb5b8a
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/2e0e74c59b2761a414d9f48d7bee1e45220b2427 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/474d6c771d798bca84f0a140b611e36743511e18 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8dbed691e43a50903658130bde0fcb5abc425b37 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/96a4713ae041cc85e712bac682cd2e644004d6c6 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/98d0912e9f841e5529a5b89a972805f34cb1c69d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/9b40bdc2a3298225dffab8158208a0d8c6300578 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/ceafb893b12f23331dcc5ff9587e643c3a40ee9f Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/fd470f0a97b8e9a125f520265d2f3b088ffb5b8a Types: Patch
      —

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

    5. Record modifiedRed Hat ADP

      Show 9 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://access.redhat.com/security/cve/CVE-2026-52943
      Referenceadded
      —
      https://bugzilla.redhat.com/show_bug.cgi?id=2492137
      Referenceadded
      —
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52943.json
      Referenceremoved
      https://access.redhat.com/security/cve/CVE-2026-52943
      —
      Referenceremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2492137
      —
      Referenceremoved
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52943.json
      —
      Reference typeremoved
      https://access.redhat.com/security/cve/CVE-2026-52943 Types: Third Party Advisory
      —
      Reference typeremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2492137 Types: Third Party Advisory
      —
      Reference typeremoved
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52943.json Types: Third Party Advisory
      —

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

    Show 2 older changes

    1. 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/2026/52xxx/CVE-2026-52943.json">CVE-2026-52943</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html

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

    2. ReceivedLinux

      Description added or changed

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Linux, Linux
      Descriptionadded
      —
      In the Linux kernel, the following vulnerability has been resolved: net: skbuff: fix missing zerocopy reference in pskb_carve helpers pskb_carve_inside_header() and pskb_carve_inside_nonlinear() both copy the old skb_shared_info header into a new buffer via memcpy(), which includes the destructor_arg pointer (uarg) for MSG_ZEROCOPY skbs. Neither function calls net_zcopy_get() for the new shinfo, creating an unaccounted holder: every skb_shared_info with destructor_arg set will call skb_zcopy_clear() once when freed, but the corresponding net_zcopy_get() was never called for the new copy. Repeated calls drive uarg->refcnt to zero prematurely, freeing ubuf_info_msgzc while TX skbs still hold live destructor_arg pointers. KASAN reports use-after-free on a freed ubuf_info_msgzc: BUG: KASAN: slab-use-after-free in skb_release_data+0x77b/0x810 Read of size 8 at addr ffff88801574d3e8 by task poc/220 Call Trace: skb_release_data+0x77b/0x810 kfree_skb_list_reason+0x13e/0x610 skb_release_data+0x4cd/0x810 sk_skb_reason_drop+0xf3/0x340 skb_queue_purge_reason+0x282/0x440 rds_tcp_inc_free+0x1e/0x30 rds_recvmsg+0x354/0x1780 __sys_recvmsg+0xdf/0x180 Allocated by task 219: msg_zerocopy_realloc+0x157/0x7b0 tcp_sendmsg_locked+0x2892/0x3ba0 Freed by task 219: ip_recv_error+0x74a/0xb10 tcp_recvmsg+0x475/0x530 The skb consuming the late access still referenced the same uarg via shinfo->destructor_arg copied by pskb_carve_inside_nonlinear() without a refcount bump. This has been verified to be reliably exploitable: a working proof-of-concept achieves full root privilege escalation from an unprivileged local user on a default kernel configuration. The fix follows the pattern of pskb_expand_head() which has the same memcpy/cloned structure. For pskb_carve_inside_header(), net_zcopy_get() is placed after skb_orphan_frags() succeeds, so the orphan error path needs no cleanup. For pskb_carve_inside_nonlinear(), net_zcopy_get() is placed after all failure points and just before skb_release_data(), so no error path needs cleanup at all -- matching pskb_expand_head() more closely and avoiding the need for a balancing net_zcopy_put().
      Referenceadded
      —
      https://git.kernel.org/stable/c/2e0e74c59b2761a414d9f48d7bee1e45220b2427
      Referenceadded
      —
      https://git.kernel.org/stable/c/474d6c771d798bca84f0a140b611e36743511e18
      Referenceadded
      —
      https://git.kernel.org/stable/c/8dbed691e43a50903658130bde0fcb5abc425b37
      Referenceadded
      —
      https://git.kernel.org/stable/c/96a4713ae041cc85e712bac682cd2e644004d6c6
      Referenceadded
      —
      https://git.kernel.org/stable/c/98d0912e9f841e5529a5b89a972805f34cb1c69d
      Referenceadded
      —
      https://git.kernel.org/stable/c/9b40bdc2a3298225dffab8158208a0d8c6300578
      Referenceadded
      —
      https://git.kernel.org/stable/c/ceafb893b12f23331dcc5ff9587e643c3a40ee9f
      Referenceadded
      —
      https://git.kernel.org/stable/c/fd470f0a97b8e9a125f520265d2f3b088ffb5b8a

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

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