CVE-2026-31430 X.509: Fix out-of-bounds access when parsing extensions
An unprivileged user can trigger an out-of-bounds read in the Linux kernel X.509 parser via a crafted certificate, potentially causing a crash or leaking memory.
- 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-2026-31430?
CVE-2026-31430 is a high-severity memory corruption vulnerability in Linux kernel, published on 20 Apr 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:
X.509: Fix out-of-bounds access when parsing extensions
Leo reports an out-of-bounds access when parsing a certificate with empty Basic Constraints or Key Usage extension because the first byte of the extension is read before checking its length. Fix it.
The bug can be triggered by an unprivileged user by submitting a specially crafted certificate to the kernel through the keyrings(7) API. Leo has demonstrated this with a proof-of-concept program responsibly disclosed off-list.
Weakness: CWE-125
Which versions are affected by CVE-2026-31430?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31430?
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-2026-31430 being exploited?
There is no known exploitation of CVE-2026-31430 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-83096, BELL-CVE-2026-31430, DEBIAN-CVE-2026-31430, GHSA-q7h9-pvj5-g9fp, ROOT-OS-DEBIAN-13-CVE-2026-31430, ROOT-OS-UBUNTU-2404-CVE-2026-31430 and 1 more.