HighCVE-2026-23273

    Linux Kernel: Use-After-Free (CVE-2026-23273)

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

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: macvlan: observe an RCU grace period in macvlan_common_newlink() error path valis reported that a race condition still happens after my prior patch. macvlan_common_newlink() might have made @dev visible before detecting an error, and its caller will directly call free_netdev(dev). We must respect an RCU period, either in macvlan or the core networking stack.

    Update Linux Kernel to version 5.10.252, Linux Kernel to version 5.15.202, Linux Kernel to version 6.1.165.

    Affected
    • Linux Kernel lt 5.10.250..5.10.252
    • Linux Kernel lt 5.15.200..5.15.202
    • Linux Kernel lt 6.1.163..6.1.165
    • Linux Kernel lt 6.6.124..6.6.128
    • Linux Kernel lt 6.12.70..6.12.75
    • Linux Kernel lt 6.18.10..6.18.14
    • Linux Kernel lt 6.19..6.19.4
    • Linux Kernel lt 6.20..7.0
    Fixed in
    • Linux Kernel 5.10.252
    • Linux Kernel 5.15.202
    • Linux Kernel 6.1.165
    • Linux Kernel 6.6.128
    • Linux Kernel 6.12.75
    • Linux Kernel 6.18.14
    • Linux Kernel 6.19.4
    • Linux Kernel 7.0

    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, Debian, Ubuntu, SUSE, BSI, CVE.org, EUVD

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.8

    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
    54.41 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
    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
    0.1 %
    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
    2.8
    Low — this CVE sits in the lower 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-362

    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: macvlan: observe an RCU grace period in macvlan_common_newlink() error path valis reported that a race condition still happens after my prior patch. macvlan_common_newlink() might have made @dev visible before detecting an error, and its caller will directly call free_netdev(dev). We must respect an RCU period, either in macvlan or the core networking stack. After adding a temporary mdelay(1000) in macvlan_forward_source_one() to open the race window, valis repro was: ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2 ip link add mv0 link p2 type macvlan mode source (ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20 &) ; sleep 0.5 ; ping -c1 -I p1 1.2.3.4 PING 1.2.3.4 (1.2.3.4): 56 data bytes RTNETLINK answers: Invalid argument BUG: KASAN: slab-use-after-free in macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) Read of size 8 at addr ffff888016bb89c0 by task e/175 CPU: 1 UID: 1000 PID: 175 Comm: e Not tainted 6.19.0-rc8+ #33 NONE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:123) print_report (mm/kasan/report.c:379 mm/kasan/report.c:482) ? macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) kasan_report (mm/kasan/report.c:597) ? macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) macvlan_forward_source (drivers/net/macvlan.c:408 drivers/net/macvlan.c:444) ? tasklet_init (kernel/softirq.c:983) macvlan_handle_frame (drivers/net/macvlan.c:501) Allocated by task 169: kasan_save_stack (mm/kasan/common.c:58) kasan_save_track (./arch/x86/include/asm/current.h:25 mm/kasan/common.c:70 mm/kasan/common.c:79) __kasan_kmalloc (mm/kasan/common.c:419) __kvmalloc_node_noprof (./include/linux/kasan.h:263 mm/slub.c:5657 mm/slub.c:7140) alloc_netdev_mqs (net/core/dev.c:12012) rtnl_create_link (net/core/rtnetlink.c:3648) rtnl_newlink (net/core/rtnetlink.c:3830 net/core/rtnetlink.c:3957 net/core/rtnetlink.c:4072) rtnetlink_rcv_msg (net/core/rtnetlink.c:6958) netlink_rcv_skb (net/netlink/af_netlink.c:2550) netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sys_sendto (net/socket.c:727 net/socket.c:742 net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:131) Freed by task 169: kasan_save_stack (mm/kasan/common.c:58) kasan_save_track (./arch/x86/include/asm/current.h:25 mm/kasan/common.c:70 mm/kasan/common.c:79) kasan_save_free_info (mm/kasan/generic.c:587) __kasan_slab_free (mm/kasan/common.c:287) kfree (mm/slub.c:6674 mm/slub.c:6882) rtnl_newlink (net/core/rtnetlink.c:3845 net/core/rtnetlink.c:3957 net/core/rtnetlink.c:4072) rtnetlink_rcv_msg (net/core/rtnetlink.c:6958) netlink_rcv_skb (net/netlink/af_netlink.c:2550) netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344) netlink_sendmsg (net/netlink/af_netlink.c:1894) __sys_sendto (net/socket.c:727 net/socket.c:742 net/socket.c:2206) __x64_sys_sendto (net/socket.c:2209) do_syscall_64 (arch/x86/entry/syscall_64.c:63 arch/x86/entry/syscall_64.c:94) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:131)

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

    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
    • 6.1.163 – < 6.1.165
    • 6.6.124 – < 6.6.128
    • 6.19 – < 6.19.4
    • 5.15.200 – < 5.15.202
    • 6.18.10 – < 6.18.14
    • 5.10.250 – < 5.10.252
    • 6.20 – < 7.0
    • 6.12.70 – < 6.12.75
    • 6.1.165
    • 6.6.128
    • 6.19.4
    • 5.15.202
    • 6.18.14
    • 5.10.252
    • 7.0
    • 6.12.75
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinuxtrixie
    Linuxdebianlinux-6.1bullseye
    Linuxlinuxlinux_kernel—

    Weakness classes (CWE)

    • CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

      Class

      The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

      Entry at MITRE CWE-362

    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-362

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Weakness type (CWE)added
      —
      CWE-362

      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-2026-23273","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:07:13.078861Z"}

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

    3. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/19c7d8ac51988d053709c1e85bd8482076af845d
      Referenceadded
      —
      https://git.kernel.org/stable/c/1e58ae87ad1e6e24368dea9aec9048c758cd0e2b
      Referenceadded
      —
      https://git.kernel.org/stable/c/3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4
      Referenceadded
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      https://git.kernel.org/stable/c/721eb342d9ba19bad5c4815ea3921465158b7362
      Referenceadded
      —
      https://git.kernel.org/stable/c/91e4ff8d966978901630fc29582c1a76d3c6e46c
      Referenceadded
      —
      https://git.kernel.org/stable/c/a1f686d273d129b45712d95f4095843b864466bd
      Referenceadded
      —
      https://git.kernel.org/stable/c/d34f7a8aa9a25b7e64e0e46e444697c0f702374d
      Referenceadded
      —
      https://git.kernel.org/stable/c/e3f000f0dee1bfab52e2e61ca6a3835d9e187e35
      Referenceremoved
      https://git.kernel.org/stable/c/19c7d8ac51988d053709c1e85bd8482076af845d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/1e58ae87ad1e6e24368dea9aec9048c758cd0e2b
      —
      Referenceremoved
      https://git.kernel.org/stable/c/3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4
      —
      Referenceremoved
      https://git.kernel.org/stable/c/721eb342d9ba19bad5c4815ea3921465158b7362
      —
      Referenceremoved
      https://git.kernel.org/stable/c/91e4ff8d966978901630fc29582c1a76d3c6e46c
      —
      Referenceremoved
      https://git.kernel.org/stable/c/a1f686d273d129b45712d95f4095843b864466bd
      —
      Referenceremoved
      https://git.kernel.org/stable/c/d34f7a8aa9a25b7e64e0e46e444697c0f702374d
      —
      Referenceremoved
      https://git.kernel.org/stable/c/e3f000f0dee1bfab52e2e61ca6a3835d9e187e35
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/19c7d8ac51988d053709c1e85bd8482076af845d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/1e58ae87ad1e6e24368dea9aec9048c758cd0e2b Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/3d94323c80d7fc4da5f10f9bb06a45d39d5d3cc4 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/721eb342d9ba19bad5c4815ea3921465158b7362 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/91e4ff8d966978901630fc29582c1a76d3c6e46c Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/a1f686d273d129b45712d95f4095843b864466bd Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/d34f7a8aa9a25b7e64e0e46e444697c0f702374d Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/e3f000f0dee1bfab52e2e61ca6a3835d9e187e35 Types: Patch
      —

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

    4. Record modifiedSiemens ADP

      Show 7 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/2026/23xxx/CVE-2026-23273.json">CVE-2026-23273</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html
      —
      Referenceremoved
      https://cert-portal.siemens.com/productcert/html/ssa-082556.html
      —

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

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