CVE-2026-9539: Freedesktop.org Libslirp

Medium severity, CVSS 6.5. EPSS: 0.2% chance of exploitation in the next 30 days.

An out-of-bounds heap read and integer underflow in the TCP urgent data handling (sosendoob) in freedesktop.org libslirp version before v4.9.2 on hypervisor host environments (e.g., QEMU) allows a privileged guest VM attacker (root or CAP_NET_RAW) to leak gigabytes of sensitive host-process heap memory via sending crafted TCP segments with manipulated URG flags and urgent pointers (ti_urp).

Affected products

• Freedesktop.org Libslirp: before 4.9.2 (fixed in 4.9.2)

Published 2026-06-24. Last modified 2026-06-25.