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CVE-2026-23001 Linux CVE debrief

A use-after-free vulnerability was found in the Linux kernel's macvlan_forward_source() function. This issue arises from a lack of RCU protection on the (struct macvlan_source_entry)->vlan pointer, which can lead to a use-after-free error when macvlan_hash_del_source() is called. The vulnerability has been resolved by adding RCU protection. This vulnerability affects Linux kernel developers and maintainers, Linux distribution maintainers, and users of Linux-based systems, who should assess the impact on their systems and prioritize patching accordingly. The vulnerability has a high CVSS score of 7.8, indicating a significant risk to affected systems.

Vendor
Linux
Product
Unknown
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-01-25
Original CVE updated
2026-10-19
Advisory published
2026-01-25
Advisory updated
2026-10-19

Who should care

Linux kernel developers and maintainers, Linux distribution maintainers, and users of Linux-based systems should assess the impact of this vulnerability on their systems and prioritize patching accordingly.

Why it matters

This vulnerability has a high CVSS score of 7.8 and can potentially lead to denial-of-service attacks, elevation of privileges, or data tampering on affected Linux-based systems. Linux kernel developers, maintainers, and users should prioritize patching to prevent potential exploitation.

  • Potential denial-of-service (DoS) attacks
  • Elevation of privileges on affected systems
  • Data tampering or unauthorized access

Technical summary

The Linux kernel's macvlan_forward_source() function was vulnerable to a use-after-free error due to a lack of RCU protection on the (struct macvlan_source_entry)->vlan pointer. This issue has been resolved by adding RCU protection, ensuring that the pointer is not accessed after it has been freed. The vulnerability was addressed by modifying the macvlan_hash_del_source() function to clear the entry->vlan pointer before RCU grace period starts, preventing use-after-free errors. This change allows macvlan_forward_source() to safely skip over entries queued for freeing.

Defensive priority

Medium

Recommended defensive actions

  • Review and apply the provided patches to ensure the vulnerability is addressed.
  • Monitor Linux kernel updates for further information on the vulnerability and its resolution.
  • Assess the impact of the vulnerability on your Linux-based systems and prioritize patching accordingly.
  • Perform a thorough review of system configurations and apply compensating controls if necessary.
  • Track and monitor system logs for potential exploitation attempts.
  • Inventory and update affected assets with the latest security patches.
  • Implement additional security measures such as network segmentation or access controls.

Evidence notes

The CVE record and source item provide details about the vulnerability and its resolution. The Linux kernel's macvlan_forward_source() function was vulnerable to a use-after-free error. The issue has been addressed by adding RCU protection on the (struct macvlan_source_entry)->vlan pointer.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-23001 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-23001

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-23001 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-23001

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • macvlan: fix possible UAF in macvlan_forward_source()

    Unverified legacy reference

    URL: https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/23xxx/CVE-2026-23001.json

    cve_program_cvelist_v5

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/8133e85b8a3ec9f10d861e0002ec6037256e987e

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/484919832e2db6ce1e8add92c469e5d459a516b5

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/232afc74a6dde0fe1830988e5827921f5ec9bb3f

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/15f6faf36e162532bec5cc05eb3fc622108bf2ed

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/8518712a2ca952d6da2238c6f0a16b4ae5ea3f13

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/6dbead9c7677186f22b7981dd085a0feec1f038e

    Supplemental source

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/7470a7a63dc162f07c26dbf960e41ee1e248d80e

    Supplemental source

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.