CVE-2026-99256: dm cache: fix issue with background work locking
CVE-2026-99256 is a vulnerability in dm cache: fix issue with background work locking, rated Low by Microsoft, with a CVSS 3.1 base score of 2.3 (Low). An attacker can exploit it by an attacker with local access, with high privileges and without user interaction. Microsoft has not reported exploitation in the wild. The EPSS model estimates a 0.20% probability of exploitation activity in the next 30 days, higher than 10% of all scored vulnerabilities. Microsoft released the fix on 4 November 2026, outside Patch Tuesday. It affects 1 product in 1 product family (Open Source Software).
Key facts
- CVE ID
- CVE-2026-99256
- Severity
- Low CVSS 2.3
- Microsoft severity
- Low
- Exploited in the wild
- No
- Publicly disclosed
- No
- EPSS
- 0.20% (percentile 10%)
- 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-2026-99256 at 2.3 (temporal 2.3) using CVSS 3.1. Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
| Metric | Value |
|---|---|
| Attack vector | Local |
| Attack complexity | Low |
| Privileges required | High |
| User interaction | None |
| Scope | Unchanged |
| Confidentiality impact | None |
| Integrity impact | None |
| Availability impact | Low |
Affected products (1)
Open Source Software
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 | Release Notes | Security Update |
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. | |
| 2.0 | Information published. |