CVE-2026-72428 bpf: Fix stack slot index in nospec checks
A flaw in Linux kernel BPF nospec checks allows bypassing Spectre v4 sanitization, potentially exposing sensitive data to local attackers.
- 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-2026-72428?
CVE-2026-72428 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 stack slot index in nospec checks
check_stack_write_fixed_off() computes the byte slot for a fixed-offset stack write as -off - 1, and records each written byte in slot_type[] with (slot - i) % BPF_REG_SIZE.
The Spectre v4 sanitization pre-check uses slot_type[i] instead. For a 4-byte write at fp-8 after the lower half of fp-8 has been zeroed, the pre-check scans bytes 0..3 and sees STACK_ZERO while the actual write updates bytes 7..4. That can leave the second half-slot write without nospec_result even though the bytes being overwritten still require sanitization.
Use the same slot index in the sanitization pre-check that the write path uses when updating slot_type[].
Which versions are affected by CVE-2026-72428?
How do I fix CVE-2026-72428?
Apply the vendor's patch.
Is CVE-2026-72428 being exploited?
There is no known exploitation of CVE-2026-72428 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72428, DEBIAN-CVE-2026-72428, GHSA-xwq5-6xrg-83hr, UBUNTU-CVE-2026-72428.