Quick answers
- Is CVE-2026-86140 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-86140 being exploited in the wild.
- How severe is CVE-2026-86140?
- High severity, with a CVSS score of 8, published 5 September 2026.
- Which products and versions are affected?
- GNOME libxml2 before 2.15.4.
- Is there a fix for CVE-2026-86140?
- A patch was published on 2026-09-05: fixed in version 2.15.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-86140 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-86140?
- Check whether you run Xmlsoft Libxml2. 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
The vulnerability is a stack-based buffer overflow in the xmlSnprintfElements function in valid.c, caused by unchecked strcat() calls that write to a fixed-size buffer without bounds checking. The vulnerable code calls strcat(buf, "(") and strcat(buf, ")") without verifying that sufficient space remains in the buffer. An attacker can trigger this by providing malformed XML with deeply nested or specially constructed element definitions that cause the buffer to overflow. The vulnerability was patched in version 2.15.4 by adding remaining-space checks before both strcat calls, returning early with ellipsis notation when buffer space is insufficient. No active exploitation in the wild has been reported.
Affected products
- GNOME libxml2 before 2.15.4
Timeline
- 2026-09-05: disclosed
- 2026-09-05: patched: fixed in version 2.15.4