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CVE-2026-46212 Linux CVE debrief

A use-after-free vulnerability exists in the Linux kernel's batman-adv (Better Approach To Mobile Ad-hoc Networking) subsystem, specifically within the Bridge Loop Avoidance (BLA) component. The flaw occurs in batadv_bla_del_backbone_claims() when removing claims for a backbone gateway. The function incorrectly drops the reference count via batadv_claim_put() before completing all accesses to the claim object, potentially causing premature memory deallocation by batadv_claim_release() while the hash list entry is still being processed. This race condition could lead to kernel memory corruption or denial of service. The vulnerability affects systems using batman-adv mesh networking with BLA enabled. Multiple stable kernel branches have received patches.

Vendor
Linux
Product
Unknown
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-28
Original CVE updated
2026-06-10
Advisory published
2026-05-28
Advisory updated
2026-06-10

Who should care

Linux system administrators operating batman-adv mesh networks, kernel maintainers for distributions shipping batman-adv, network infrastructure teams relying on wireless mesh deployments using BLA for loop prevention

Technical summary

The vulnerability is a use-after-free condition in net/batman-adv/bridge_loop_avoidance.c. When batadv_bla_del_backbone_claims() iterates through claims to remove them for a backbone gateway, it calls batadv_claim_put() to drop the reference held by the hash list entry. However, this reference drop occurs before the final access to the claim object completes. If batadv_claim_release() executes and frees the claim memory while the function still requires access to the list entry or claim data, undefined behavior occurs. The fix reorders operations to ensure the hash list entry removal and final claim access complete before the reference count is decremented.

Defensive priority

high

Recommended defensive actions

  • Apply kernel updates from official Linux stable repositories containing the identified fixes
  • Verify batman-adv BLA functionality remains operational after patching
  • Monitor kernel logs for memory corruption indicators on systems running batman-adv mesh networks
  • Review systems using batman-adv for mesh networking deployments and prioritize patching for production infrastructure
  • Consider disabling batman-adv BLA functionality temporarily if patching is not immediately feasible and the feature is not required

Evidence notes

Vulnerability description sourced from official CVE record and NVD entry. Technical details derived from kernel commit messages describing the use-after-free condition in batadv_bla_del_backbone_claims(). Five stable kernel patches identified across different release branches.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-46212 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-46212

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

  • CVE-2026-46212 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-46212

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

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/00155f336a5e8b1006d2ca9ae7ad8fc4a44bb401

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/0cc9847c64cb6e61118bc78c9187c8209a7197fa

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/368449e467d5f1e2c2e987bf2bd57000ba75e10b

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/4ae1709a314060a196981b344610d023ea841e57

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/6c5dc6d68e6ba7f0224a757a39ed52fcdb54d472

    416baaa9-dc9f-4396-8d5f-8c081fb06d67

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.