CVE-2026-74337 bpf: Fix NMI/tracepoint re-entry deadlock on lru locks
A race condition in Linux kernel BPF LRU locks allows local attackers to cause a deadlock and system denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74337?
CVE-2026-74337 is a vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix NMI/tracepoint re-entry deadlock on lru locks
NMI and tracepoint BPF programs can re-enter the per-CPU or global LRU lock that bpf_lru_pop_free()/push_free() already hold on the same CPU, AA-deadlocking. Lockdep reports "inconsistent {INITIAL USE} -> {IN-NMI}" on &l->lock (syzbot c69a0a2c816716f1e0d5) and "possible recursive locking detected" on &loc_l->lock (syzbot 18b26edb69b2e19f3b33).
Prior trylock and rqspinlock based fixes (see links) were nacked because compromised on reliability.
This patch converts every LRU lock site to rqspinlock_t and adds a recovery path for some failure windows to avoid node leaks.
Failure recovery:
- *_pop_free top-level: return NULL; prealloc_lru_pop() already treats that as no-free-element (-ENOMEM).
- Cross-CPU steal: skip the victim's locked loc_l, try next CPU.
- Post-steal local lock fail: publish stolen node to lockless per-CPU free_llist; next pop on this CPU picks it up.
- push_free fail: mark node pending_free=1. __local_list_flush(), __local_list_pop_pending() reclaim the node from pending_list. __bpf_lru_list_shrink_inactive() reclaims the node from inactive list. Nodes from active list are reclaimed by __bpf_lru_list_shrink() or after __bpf_lru_list_rotate_active() demotes it to the inactive.
Which versions are affected by CVE-2026-74337?
How do I fix CVE-2026-74337?
Apply the vendor's patch.
Is CVE-2026-74337 being exploited?
There is no known exploitation of CVE-2026-74337 in the wild and no public exploit code.
Sources
Also known as AZL-110429, BELL-CVE-2026-74337, DEBIAN-CVE-2026-74337, GHSA-x3mj-vjph-62qr, UBUNTU-CVE-2026-74337.