Vulnerability · Published Jun 24, 2026 · Assigned by STAR_Labs
CVE-2026-9539libslirp TCP URG OOB Read Information Leak
Medium 6.5
In plain English
A medium-severity out-of-bounds read in libslirp from freedesktop.org. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 13% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libslirp | no fix listed | DEBIAN-CVE-2026-9539 |
| Debian:13 | libslirp | 4.8.0-1+deb13u1 | DEBIAN-CVE-2026-9539 |
| Debian:14 | libslirp | 4.9.2-1 | DEBIAN-CVE-2026-9539 |
| Ubuntu:22.04:LTS | libslirp | 4.6.1-1ubuntu0.2 | UBUNTU-CVE-2026-9539 |
| Ubuntu:22.04:LTS | libslirp | 4.6.1-1ubuntu0.2 | USN-8550-1 |
| Ubuntu:24.04:LTS | libslirp | 4.7.0-1ubuntu3.1 | USN-8550-1 |
| Ubuntu:24.04:LTS | libslirp | 4.7.0-1ubuntu3.1 | UBUNTU-CVE-2026-9539 |
| Ubuntu:25.10 | libslirp | no fix listed | UBUNTU-CVE-2026-9539 |
| Ubuntu:26.04:LTS | libslirp | 4.9.1-1ubuntu1.1 | USN-8550-1 |
| Ubuntu:26.04:LTS | libslirp | 4.9.1-1ubuntu1.1 | UBUNTU-CVE-2026-9539 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| freedesktop.org | libslirp | 0 – before 4.9.2 |
Weakness: CWE-125 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N