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CVE-2026-72322 Linux CVE debrief

A race condition exists between device teardown and incoming MLD query processing in the Linux kernel, leading to a Use-After-Free in the MLD delayed work. During device destruction, the primary reference to inet6_dev is dropped, which can drop its refcount to 0. The actual freeing of inet6_dev memory is deferred via RCU. Concurrently, the packet receive path runs under RCU read lock and obtains the inet6_dev pointer. Because the memory is RCU-protected, CPU-0 can safely dereference inet6_dev even if its refcount has hit 0. However, if CPU-0 calls igmp6_event_query() and schedules delayed work, it attempts to acquire a reference using in6_dev_hold(). This increments the refcount from 0 to 1, triggering a 'refcount_t: addition on 0' warning. Since the inet6_dev memory is still scheduled to be freed after the RCU grace period, the device is freed while the work is still scheduled. When the work runs, it accesses the freed memory, causing a kernel panic. Fix this by using refcount_inc_not_zero() (via a new helper in6_dev_hold_safe()) to prevent acquiring a reference if the device is already being destroyed.

Vendor
Linux
Product
Unknown
CVSS
Unknown
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-15
Original CVE updated
2026-08-15
Advisory published
2026-08-15
Advisory updated
2026-08-15

Who should care

Linux kernel developers and maintainers, Linux distribution vendors, and organizations using Linux-based systems, particularly those with networked devices and MLD query processing enabled, should review and apply the kernel patch to prevent exploitation. Additionally, Linux system administrators and security teams should inventory systems for exposure, prioritize patching based on criticality, and monitor for suspicious MLD query processing activity.

Technical summary

The Linux kernel vulnerability CVE-2026-72322 arises from a race condition between device teardown and incoming MLD query processing, leading to a Use-After-Free in the MLD delayed work. During device destruction, the primary reference to inet6_dev is dropped, which can drop its refcount to 0. The actual freeing of inet6_dev memory is deferred via RCU. Concurrently, the packet receive path runs under RCU read lock and obtains the inet6_dev pointer. The fix involves using refcount_inc_not_zero() to prevent acquiring a reference if the device is already being destroyed.

Defensive priority

High

Recommended defensive actions

  • Apply the kernel patch to update the refcount handling in inet6_dev.
  • Inventory Linux systems for exposure and prioritize patching based on criticality.
  • Monitor for suspicious MLD query processing activity.
  • Implement compensating controls such as rate limiting MLD queries.
  • Exception tracking for systems with custom kernel modules.

Evidence notes

The Linux kernel vulnerability CVE-2026-72322 has been resolved. A race condition exists between device teardown and incoming MLD query processing, leading to a Use-After-Free in the MLD delayed work. The issue arises from the incorrect handling of inet6_dev references during device destruction and concurrent MLD query processing. The fix involves using refcount_inc_not_zero() to prevent acquiring a reference if the device is already being destroyed.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-72322 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-72322

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

  • CVE-2026-72322 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-72322

    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/0401d6cf7877c9be36652385dfcbf7f891b8b590

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/0458ba1cda830ba4ccfcd9e19c0891438bcdbe4e

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9815e834f5ff8b39e0ea9f0dbd532f4a3b8f0785

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9b26518b6896a16b809b1e42986f4ebac7bccc1e

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/9ce741c22df4fd9546e30306317ac7df3607e48f

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/ebbebf6cee950d7f1c81990256c0eae9e62572ae

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

  • Source reference

    Unverified legacy reference

    URL: https://git.kernel.org/stable/c/f03b0a45535d49bdab7e502efaacee205b2a7865

    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.