Quick answers
- Is CVE-2026-56403 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-56403 being exploited in the wild.
- How severe is CVE-2026-56403?
- Medium severity, with a CVSS score of 6.9, published 21 June 2026.
- Which products and versions are affected?
- Libexpat Project Expat before 2.8.2.
- Is there a fix for CVE-2026-56403?
- A patch was published on 2026-05-22: Fix merged into master branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-56403 attacked?
- It is attacked with local access, in a software library.
- Am I affected by CVE-2026-56403?
- Check whether you run Libexpat Project Expat at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
An integer overflow vulnerability (CWE-190) exists in the 'storeAtts' function within libexpat's xmlparse.c before version 2.8.2. The flaw occurs when calculating lengths for attribute prefixes and URIs, where signed integer arithmetic can wrap around if provided with specially crafted XML input. An attacker with the ability to provide local XML files for parsing could exploit this to cause memory corruption, potentially leading to a compromise of confidentiality and integrity. The issue is addressed in version 2.8.2 by adding explicit bounds checks against INT_MAX before performing addition and subtraction on length variables.
Affected products
- libexpat project libexpat before 2.8.2
Timeline
- 2026-05-22: patched: Fix merged into master branch
- 2026-06-21: disclosed: CVE published