CVE-2026-93173 bpf,lsm: Drop bpf_prog_free from sleepable_lsm_hooks
A local attacker with high privileges can trigger a kernel bug causing a system crash when freeing BPF programs attached to sleepable LSM hooks.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93173?
CVE-2026-93173 is a denial of service vulnerability in Linux, published on 17 Sep 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,lsm: Drop bpf_prog_free from sleepable_lsm_hooks
__bpf_prog_put_rcu() is the call_rcu() callback for non-sleepable programs. security_bpf_prog_free() called from there fires bpf_prog_free in softirq; if a sleepable LSM prog is attached to that hook, might_fault() BUGs:
BUG: sleeping function called from invalid context in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 5038 preempt_count: 101, expected: 0 Call Trace: <IRQ> __bpf_prog_enter_sleepable+0x1cd/0x320 kernel/bpf/trampoline.c:1255 bpf_trampoline_6442549705+0x53/0xd7 security_bpf_prog_free+0xde/0x130 security/security.c:5465 __bpf_prog_put_rcu+0xab/0xd0 kernel/bpf/syscall.c:2365 rcu_do_batch kernel/rcu/tree.c:2617 [inline] handle_softirqs+0x236/0x800 kernel/softirq.c:622 </IRQ>
The call_rcu/call_rcu_tasks_trace split reflects the freed program's sleepability, not that of any attached observer.
security_bpf_prog_free() also frees prog->aux->security, which has to stay after the grace period, so drop bpf_prog_free from sleepable_lsm_hooks rather than move the call. Non-sleepable observers still run there.
Which versions are affected by CVE-2026-93173?
How do I fix CVE-2026-93173?
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-2026-93173 being exploited?
There is no known exploitation of CVE-2026-93173 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-93173, DEBIAN-CVE-2026-93173, GHSA-ggp7-x9rm-wrm3, UBUNTU-CVE-2026-93173.