Quick answers
- Is CVE-2026-86143 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-86143 being exploited in the wild.
- How severe is CVE-2026-86143?
- Medium severity, with a CVSS score of 6.9, published 5 September 2026.
- Which products and versions are affected?
- GNOME libxml2 before 2.15.4.
- Is there a fix for CVE-2026-86143?
- A patch was published on 2026-09-05: Fix available in libxml2 2.15.4 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-86143 attacked?
- It is attacked with local access, in a software library.
- Am I affected by CVE-2026-86143?
- 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 an integer overflow flaw in the xmlIO module of libxml2, specifically in the xmlOutputWriteCallback and xmlBufUse functions. The code fails to validate that a calculated length value has not overflowed to negative before passing it to registered write callbacks, allowing negative lengths to reach callback handlers. This occurs in xmlOutputBufferWrite when buffer length calculations overflow. An attacker who can control XML input processed by a vulnerable application may trigger the overflow and potentially cause memory corruption or leakage through the misuse of negative lengths in callback functions. The fix was introduced in libxml2 version 2.15.4 by adding integer overflow checks before the write callback is invoked.
Affected products
- GNOME libxml2 before 2.15.4
Timeline
- 2026-09-05: disclosed
- 2026-09-05: patched: Fix available in libxml2 2.15.4