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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.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-08-15T06:22:05.207Z and has not been modified since then.