CVE-2026-72423 bpf: Guard conntrack opts error writes
A missing bounds check in Linux kernel BPF conntrack kfuncs allows out-of-bounds writes, potentially enabling privilege escalation or 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-2026-72423?
CVE-2026-72423 is a high-severity memory corruption 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: Guard conntrack opts error writes
The conntrack lookup and allocation kfuncs take an opts pointer together with an opts__sz argument. The verifier checks only the memory range described by opts__sz, but the wrappers unconditionally write opts->error whenever the internal lookup or allocation helper returns an error.
For an invalid size smaller than the end of opts->error, that write can land outside the verifier-checked range. Keep returning NULL for invalid arguments, but only report the error through opts->error when the supplied size includes the field.
This preserves error reporting for the supported 12-byte and 16-byte layouts, and for other invalid sizes that still include opts->error.
Which versions are affected by CVE-2026-72423?
How do I fix CVE-2026-72423?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-72423 being exploited?
There is no known exploitation of CVE-2026-72423 in the wild and no public exploit code.
Sources
Also known as AZL-96057, BELL-CVE-2026-72423, DEBIAN-CVE-2026-72423, GHSA-x2j2-wxw5-pjr8, UBUNTU-CVE-2026-72423.