What’s Vulnerable › Vulnerabilities

CVE-2026-9539: libslirp TCP URG OOB Read Information Leak

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-24 · updated 2026-10-25
• Weakness: CWE-125

Description

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

How to fix

Upgrade to a fixed version: freedesktop.org libslirp 4.9.2. Check the vendor advisory for mitigations.

References

• https://gitlab.freedesktop.org/slirp/libslirp/-/commit/927bca7344e31fd58e2f7afaca784aad4400eb84
• https://gitlab.freedesktop.org/slirp/libslirp/-/releases/v4.9.2
• https://gitlab.freedesktop.org/slirp/libslirp/-/work_items/93
• https://gitlab.freedesktop.org/slirp/libslirp/-/work_items/93

Get alerted when CVE-2026-9539 or the next vulnerability affects your stack