# CVE-2026-40469: Heap buffer overflow in gawk

> An integer overflow in gawk's do_sub routine allows attackers to crash the program via heap metadata corruption on 32-bit builds.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 Jul 2026
- **Updated:** 13 Jul 2026
- **Also known as:** BELL-CVE-2026-40469, CLSA-2026-1784303038, CLSA-2026-1787229301, CLSA-2026-1792441187, DEBIAN-CVE-2026-40469, ECHO-e2f2-918d-5b78, GHSA-5x2x-26c9-4q5x, JLSEC-2026-787, UBUNTU-CVE-2026-40469

## What is CVE-2026-40469?

CVE-2026-40469 is a medium-severity vulnerability in GNU gawk, published on 13 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Integer overflow vulnerability has been found in "builtin.c" program file of gawk (do_sub() routine). This issue could be used to overwrite gawk heap metadata and objects causing the program to crash. It affects 32-bit builds of gawk in versions 5.4.0 and below.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-40469?

It affects 1 product.


Products: Fossies Gawk.

## How do I fix CVE-2026-40469?

Apply the vendor's patch.

## Is CVE-2026-40469 being exploited?

There is no known exploitation of CVE-2026-40469 in the wild and no public exploit code.

## Other vulnerabilities in GNU gawk

- [CVE-2026-40467](https://insights.sbomify.com/CVE-2026-40467/): Use after free in gawk (medium 5.1)
- [CVE-2026-40553](https://insights.sbomify.com/CVE-2026-40553/): Stack-based buffer overflow in gawk (medium 5.1)
- [CVE-2026-40468](https://insights.sbomify.com/CVE-2026-40468/): Heap buffer overflow in gawk (low 2.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40469 and fix it if it is affected.

What it is: CVE-2026-40469 is a medium-severity vulnerability in GNU gawk, published on 13 Jul 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-2026-40469 in the wild and no public exploit code.

Affected product: GNU gawk. 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-2026-40469/ (Markdown: https://insights.sbomify.com/CVE-2026-40469/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40469
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40469
- OSV: https://osv.dev/vulnerability/CVE-2026-40469

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40469/
Summaries are generated and may contain mistakes; the official description above is the record.