libslirp TCP URG OOB Read Information Leak
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Information disclosure
- Confidentiality · integrity · availability
- High · None · None
- Fix status
- Partial Red Hat: 2 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-125 and the CVSS impact.
Summary
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).
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| [freedesktop.org] | libslirp | before 4.9.2 | 4.9.2 | Patch available | CNA |
- libslirp Vendor[freedesktop.org] Affected before 4.9.2 Fixed in 4.9.2 Patch available CNA
Remediation
- Fix · CNA libslirp (freedesktop.org) Fixed in 4.9.2
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenShift Container Platform 4 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift Container Platform 5 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-9539
- 2026-10-03 Alias added: GHSA-4243-hp56-4m7f
- 2026-10-24 Affected versions changed · Red Hat
- 2026-10-24 CVSS score added · Red Hat
- 2026-10-30 Affected versions changed · Red Hat
References
Sources
- CVE-2026-9539 · CVE Program
- CVE-2026-9539 · NVD
- FIRST EPSS
- GHSA-4243-hp56-4m7f · GitHub Advisory Database · CC BY 4.0
- CVE-2026-9539 · Red Hat security data · CC BY 4.0
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