Quick answers
- Is CVE-2026-118370 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-118370 being exploited in the wild.
- How severe is CVE-2026-118370?
- Medium severity, with a CVSS score of 5.9, published 28 October 2026.
- Which products and versions are affected?
- Libexpat through 2.9.0.
- Is there a fix for CVE-2026-118370?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-118370 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-118370?
- Check whether you run Libexpat 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
A signed integer overflow occurs in the storeAtts() function in xmlparse.c when parsing XML elements with extremely large attribute counts. An attacker can craft an XML document with a start tag carrying over 2^30 attributes; the integer variables attIndex and nPrefixes overflow, leading to out-of-bounds memory writes. No authentication or user interaction is required; the vulnerability is triggered by network-supplied XML input.
Affected products
- libexpat through 2.9.0
Timeline
- 2026-10-28: disclosed