# CVE-2026-25210: Integer overflow in libexpat

> An integer overflow in libexpat's buffer size calculation can lead to memory corruption, potentially allowing denial of service or code execution.

- **Severity:** Medium 6.9 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L`)
- **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:** 30 Jan 2026
- **Updated:** 2 Jun 2026
- **Also known as:** ALPINE-CVE-2026-25210, AZL-75815, AZL-76340, BELL-CVE-2026-25210, CLEANSTART-2026-QP18579, CLSA-2026-1773924425, CLSA-2026-1773924658, CLSA-2026-1773925534, CLSA-2026-1773926416, CLSA-2026-1773927217, CLSA-2026-1773928179, CLSA-2026-1773928447, CLSA-2026-1773930526, CLSA-2026-1773930717, CLSA-2026-1774006814, CLSA-2026-1774009875, CLSA-2026-1774021165, CLSA-2026-1774021417, CLSA-2026-1774283473, DEBIAN-CVE-2026-25210, ECHO-d167-d9ff-f755, GHSA-857q-6v86-xp84, JLSEC-2026-380, OESA-2026-1295, OESA-2026-1296, OESA-2026-1298, OESA-2026-1378, ROOT-OS-DEBIAN-11-CVE-2026-25210

## What is CVE-2026-25210?

CVE-2026-25210 is a medium-severity vulnerability in Libexpat Project Libexpat, published on 30 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In libexpat before 2.7.4, the doContent function does not properly determine the buffer size bufSize because there is no integer overflow check for tag buffer reallocation.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-25210?

It affects 1 product.


Products: Libexpat Project Libexpat.

## How do I fix CVE-2026-25210?

Upgrade to a fixed version.

## Is CVE-2026-25210 being exploited?

There is no known exploitation of CVE-2026-25210 in the wild and no public exploit code.

## Other vulnerabilities in Libexpat Project Libexpat

- [CVE-2024-45490](https://insights.sbomify.com/CVE-2024-45490/): Integer overflow in n/a (critical 9.8)
- [CVE-2026-66046](https://insights.sbomify.com/CVE-2026-66046/): Expat Denial of Service via storeAtts() Quadratic Complexity (high 8.7)
- [CVE-2021-46143](https://insights.sbomify.com/CVE-2021-46143/): Integer overflow in n/a (high 8.1)
- [CVE-2017-11742](https://insights.sbomify.com/CVE-2017-11742/): Privilege escalation in n/a (high 7.8)
- [CVE-2025-59375](https://insights.sbomify.com/CVE-2025-59375/): Denial of service in libexpat (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-25210 and fix it if it is affected.

What it is: CVE-2026-25210 is a medium-severity vulnerability in Libexpat Project Libexpat, published on 30 Jan 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-2026-25210 in the wild and no public exploit code.

Affected product: Libexpat Project Libexpat. 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-2026-25210/ (Markdown: https://insights.sbomify.com/CVE-2026-25210/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-25210
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-25210
- OSV: https://osv.dev/vulnerability/CVE-2026-25210

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-25210/
Summaries are generated and may contain mistakes; the official description above is the record.