# 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.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H`)
- **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:** Yes
- **Published:** 20 Apr 2026
- **Updated:** 11 May 2026
- **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, UBUNTU-CVE-2026-31430

## 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 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-31430?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31430?

Apply the vendor's patch.

## 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

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31430 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-31430 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-31430/ (Markdown: https://insights.sbomify.com/CVE-2026-31430/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31430
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31430
- OSV: https://osv.dev/vulnerability/CVE-2026-31430

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31430/
Summaries are generated and may contain mistakes; the official description above is the record.