CVE-2026-90342 bpf: Fix mmap_lock deadlock on arena lock failure
A local attacker can trigger a kernel deadlock in the BPF arena fault handler, causing a system-wide 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-2026-90342?
CVE-2026-90342 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: Fix mmap_lock deadlock on arena lock failure
Reported by the Sashiko AI review.
arena_vm_fault() returns VM_FAULT_RETRY when it can't take arena->spinlock, but it never took mmap_lock. The fault path assumes a VM_FAULT_RETRY handler already dropped mmap_lock and re-takes it on the retry, so mmap_lock gets taken twice and can deadlock:
do_user_addr_fault() { fault = handle_mm_fault(...); // calls arena_vm_fault() if (fault & VM_FAULT_RETRY) goto retry; // re-locks mmap_lock mmap_read_unlock(mm); }
Return VM_FAULT_SIGBUS instead, for two reasons:
1. We could keep VM_FAULT_RETRY, but then we'd have to drop the fault lock first and cap the retry ourselves, the way __folio_lock_or_retry() does.
2. A failed raw_res_spin_lock_irqsave() already means a possible deadlock was detected, so retrying just hits the same lock again.
So returning VM_FAULT_RETRY here is overkill.
Which versions are affected by CVE-2026-90342?
How do I fix CVE-2026-90342?
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-2026-90342 being exploited?
There is no known exploitation of CVE-2026-90342 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-90342, GHSA-xw74-j5c3-43ch, UBUNTU-CVE-2026-90342.