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CVE-2026-72322

CRITICALCVSS 9.8/10EPSS 0.22%

Last modified

CVE-2026-72322 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: Fix potential UAF in MLD delayed work A race condition exists 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. EPSS estimates a 0.22% chance of exploitation in the next 30 days.

Description

In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: Fix potential UAF in MLD delayed work A race condition exists 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. 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. If the refcount is 0, we do not schedule the work.

Metrics

CVSS 3.1
9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability
0.22%

12.8th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < f12b63ef26a035c5a29b3ef56401e38199010d4a; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 0401d6cf7877c9be36652385dfcbf7f891b8b590; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < f03b0a45535d49bdab7e502efaacee205b2a7865; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 9815e834f5ff8b39e0ea9f0dbd532f4a3b8f0785; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < ebbebf6cee950d7f1c81990256c0eae9e62572ae; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 9ce741c22df4fd9546e30306317ac7df3607e48f; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 0458ba1cda830ba4ccfcd9e19c0891438bcdbe4e; >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, < 9b26518b6896a16b809b1e42986f4ebac7bccc1e
LinuxLinux2.6.12

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-72322?
In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: Fix potential UAF in MLD delayed work A race condition exists 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. 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. If the refcount is 0, we do not schedule the work.
How severe is CVE-2026-72322?
CVE-2026-72322 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.22% probability of exploitation in the next 30 days.
How do I fix CVE-2026-72322?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST