CVE-2026-56406 libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was present in XML_Parse.
Medium 6.9
Published
Updated
Check this codebase for CVE-2026-56406 and fix it if it is affected.
What it is: CVE-2026-56406 is a medium-severity vulnerability in Libexpat Project Libexpat, published on 21 Jun 2026.
Exploitation: There is no known exploitation of CVE-2026-56406 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-2026-56406/ (Markdown: https://insights.sbomify.com/CVE-2026-56406/index.md)
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-56406?
CVE-2026-56406 is a medium-severity vulnerability in Libexpat Project Libexpat, published on 21 Jun 2026.
Official description
libexpat before 2.8.2 has an integer overflow in XML_ParseBuffer because it lacked a check that was present in XML_Parse.
Weakness: CWE-190
Which versions are affected by CVE-2026-56406?
It affects 1 product.
Products include Libexpat Project Libexpat.
How do I fix CVE-2026-56406?
Upgrade to a fixed version.
Is CVE-2026-56406 being exploited?
There is no known exploitation of CVE-2026-56406 in the wild and no public exploit code.
Other vulnerabilities in Libexpat Project Libexpat
Sources
Also known as ALPINE-CVE-2026-56406, AZL-90234, BELL-CVE-2026-56406, DEBIAN-CVE-2026-56406, ECHO-8fda-fcf5-f272, GHSA-v2j6-3q6q-gm3g and 3 more.