CVE-2026-72069
In the Linux kernel, the following vulnerability has been resolved: locking/rt: Fix the incorrect RCU protection in rt_spin_unlock() rt_spin_unlock() releases the RCU protection before unlocking the lock.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.73%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
In the Linux kernel, the following vulnerability has been resolved: locking/rt: Fix the incorrect RCU protection in rt_spin_unlock() rt_spin_unlock() releases the RCU protection before unlocking the lock. That opens the door for the following UAF scenario: T1 T2 spin_lock(&p->lock); rcu_read_lock(); invalidate(p); p = rcu_dereference(ptr); rcu_assign_pointer(ptr, NULL); if (!p) return; spin_unlock(&p->lock); spin_lock(&p->lock) lock(&lock->lock); rcu_read_lock(); kfree_rcu(p); rcu_read_unlock(); .... spin_unlock(&p->lock) rcu_read_unlock(); // Ends grace period rcu_do_batch() kfree(p); UAF -> rt_mutex_cmpxchg_release(&lock->lock...) Regular spinlocks keep preemption disabled accross the unlock operation, which provides full RCU protection, but the RT substitution fails to resemble that. Same applies for the rwlock substitution. Move the rcu_read_unlock() invocation past the unlock operations to match the non-RT semantics. This makes it asymmetric vs. rt_xxx_lock(), but that's harmless as the caller needs to hold RCU read lock across the lock operation. The migrate_enable() call stays before the unlock operation because there is no per CPU operation in the unlock path which would require migration to be kept disabled.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.73% probability · 52th percentile
- CISA KEV
- Not listed
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/1f0d56d3f1e88f20f6e46109402f8c15d59bac37
- https://git.kernel.org/stable/c/3cfaac77b3c32ac3940df28866de263c3f45d24c
- https://git.kernel.org/stable/c/633cadbc0b8323f5cc140a285d2432089dbb534e
- https://git.kernel.org/stable/c/83f9fb561c1c3917e19f95523dd933c7d30291aa
- https://git.kernel.org/stable/c/89038cc87d80c77e7aa6f42a64b2573b74af339f
- https://git.kernel.org/stable/c/9d1fcd64ab81200e02b7a6db5eb1da8e244e8289
- https://git.kernel.org/stable/c/af28d801cd2db4cc7378554499bd4a5d84a5517e
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.