CVE-2026-120831: Libslirp: libslirp: queue pointer corruption in if_output() leading to denial of service
CVE-2026-120831 is a vulnerability in Libslirp: libslirp: queue pointer corruption in if_output() leading to denial of service, rated Moderate by Microsoft, with a CVSS 3.1 base score of 6.5 (Medium). An attacker can exploit it from an adjacent network, without any privileges and without user interaction. Microsoft has not reported exploitation in the wild. The EPSS model estimates a 0.27% probability of exploitation activity in the next 30 days, higher than 19% of all scored vulnerabilities. Microsoft released the fix on 5 November 2026, outside Patch Tuesday. It affects 1 product in 1 product family (Open Source Software).
Key facts
- CVE ID
- CVE-2026-120831
- Severity
- Medium CVSS 6.5
- Microsoft severity
- Moderate
- Exploited in the wild
- No
- Publicly disclosed
- No
- EPSS
- 0.27% (percentile 19%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- November 2026 Patch Tuesday
- Product families
- Open Source Software
CVSS score and vector
Microsoft scores CVE-2026-120831 at 6.5 (temporal 6) using CVSS 3.1. Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U
| Metric | Value |
|---|---|
| Attack vector | Adjacent network |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | None |
| Integrity impact | None |
| Availability impact | High |
| Exploit code maturity | Unproven |
Affected products (1)
Open Source Software
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| azl3 libslirp 4.9.6-1 on Azure Linux 3.0 | Release Notes | Security Update |
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |