CVE-2026-74338 bpf: Reject sleepable BPF_LSM_CGROUP programs at load time
A local attacker can cause a kernel crash by loading a sleepable BPF LSM cgroup program that attempts to sleep in an atomic context.
- 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-2026-74338?
CVE-2026-74338 is a high-severity denial of service 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: Reject sleepable BPF_LSM_CGROUP programs at load time
The cgroup shim runs under rcu_read_lock_dont_migrate(), so we should not attach any sleepable BPF programs there. Add support to the verifier to explicitly reject attempts to load sleepable BPF programs destined for LSM cgroup attachment.
Without this, we get the following splat from a BPF_LSM_CGROUP program marked BPF_F_SLEEPABLE attached to file_open when it calls bpf_get_dentry_xattr():
BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1567 in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 34317, name: load preempt_count: 0, expected: 0 RCU nest depth: 2, expected: 0 Call Trace: down_read+0x76/0x480 ext4_xattr_get+0x11f/0x700 __vfs_getxattr+0xf0/0x150 bpf_get_dentry_xattr+0xbb/0xf0 bpf_prog_e76a298dac9218c6_test_open+0x6a/0x85 __cgroup_bpf_run_lsm_current+0x326/0x840 bpf_trampoline_6442534646+0x62/0x14d security_file_open+0x34/0x60 do_dentry_open+0x340/0x1260 vfs_open+0x7a/0x440 path_openat+0x1bac/0x30a0
libbpf provides a .s named section variant for every sleepable program type except lsm_cgroup, reflecting that per-cgroup LSM programs are intended to only run in a non-sleepable context.
The above splat was obtained by bypassing libbpf by using bpf(2) directly.
Which versions are affected by CVE-2026-74338?
How do I fix CVE-2026-74338?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-74338 being exploited?
There is no known exploitation of CVE-2026-74338 in the wild and no public exploit code.
Sources
Also known as AZL-96018, BELL-CVE-2026-74338, DEBIAN-CVE-2026-74338, GHSA-rqq6-3pqg-qxx2, UBUNTU-CVE-2026-74338.