CVE-2026-72111 bpf: Reset register bounds before narrowing retval range in check_mem_access()
A flaw in the Linux kernel BPF verifier allows bypassing memory safety checks via stale register bounds, potentially enabling arbitrary code execution.
- 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-2026-72111?
CVE-2026-72111 is a high-severity 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: Reset register bounds before narrowing retval range in check_mem_access()
When the BPF verifier processes a context load of an LSM hook return value, it calls __mark_reg_s32_range() to narrow the register to the hook's valid range. However, __mark_reg_s32_range() intersects the new range with the register's existing bounds using max_t()/min_t() rather than replacing them.
If the destination register carries stale bounds from a prior instruction (e.g. BPF_MOV64_IMM), the intersection can produce a range narrower than reality. The verifier then believes it knows the register's exact value, while at runtime the actual hook return value is loaded, creating a verifier/runtime mismatch that can be used to bypass BPF memory safety checks.
The else branch already calls mark_reg_unknown() to reset register state before any narrowing. Apply the same reset in the is_retval path so stale bounds are cleared before __mark_reg_s32_range() intersects.
Which versions are affected by CVE-2026-72111?
How do I fix CVE-2026-72111?
Apply the vendor's patch.
Is CVE-2026-72111 being exploited?
There is no known exploitation of CVE-2026-72111 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72111, DEBIAN-CVE-2026-72111, GHSA-vhcf-p8jc-x5f6, UBUNTU-CVE-2026-72111.