# 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.

- **Severity:** High 8.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/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:** 15 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-96057, BELL-CVE-2026-72423, DEBIAN-CVE-2026-72423, GHSA-x2j2-wxw5-pjr8, UBUNTU-CVE-2026-72423

## 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.

## Is CVE-2026-72423 being exploited?

There is no known exploitation of CVE-2026-72423 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72423 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-72423 in the wild and no public exploit code.

Affected product: Linux. 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-2026-72423/ (Markdown: https://insights.sbomify.com/CVE-2026-72423/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72423
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72423
- OSV: https://osv.dev/vulnerability/CVE-2026-72423

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72423/
Summaries are generated and may contain mistakes; the official description above is the record.