Quick answers
- Is CVE-2026-120831 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-120831 being exploited in the wild.
- How severe is CVE-2026-120831?
- Medium severity, with a CVSS score of 6.5, published 3 November 2026.
- Which products and versions are affected?
- freedesktop.org libslirp.
- Is there a fix for CVE-2026-120831?
- 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-2026-120831 attacked?
- It is attacked from the adjacent network, in a software library.
- Am I affected by CVE-2026-120831?
- Check whether you run Freedesktop.Org Libslirp. 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 out-of-bounds write vulnerability exists in the if_output() function of libslirp when moving a session from the fast queue to the batch queue. The code incorrectly uses ifm->m_nextpkt instead of the session queue head when unlinking and reinserting packets, corrupting internal queue pointers. A guest virtual machine generating intentional burst traffic can trigger this condition to crash the host networking process without requiring authentication or user interaction.
Affected products
- freedesktop.org libslirp
Timeline
- 2026-11-03: disclosed