CVE-2021-20181
Publication date 1 February 2021
Last updated 18 August 2025
Ubuntu priority
Description
A race condition flaw was found in the 9pfs server implementation of QEMU up to and including 5.2.0. This flaw allows a malicious 9p client to cause a use-after-free error, potentially escalating their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity as well as system availability.
Status
| Package | Ubuntu Release | Status |
|---|---|---|
| qemu | 25.10 questing |
Fixed 1:5.2+dfsg-6ubuntu2
|
| 25.04 plucky |
Fixed 1:5.2+dfsg-6ubuntu2
|
|
| 24.04 LTS noble |
Fixed 1:5.2+dfsg-6ubuntu2
|
|
| 22.04 LTS jammy |
Fixed 1:5.2+dfsg-6ubuntu2
|
|
| 20.04 LTS focal |
Fixed 1:4.2-3ubuntu6.12
|
|
| 18.04 LTS bionic |
Fixed 1:2.11+dfsg-1ubuntu7.35
|
|
| 16.04 LTS xenial |
Fixed 1:2.5+dfsg-5ubuntu10.49
|
|
| 14.04 LTS trusty |
Vulnerable
|
|
| qemu-kvm | 25.10 questing | Not in release |
| 25.04 plucky | Not in release | |
| 24.04 LTS noble | Not in release | |
| 22.04 LTS jammy | Not in release | |
| 20.04 LTS focal | Not in release | |
| 18.04 LTS bionic | Not in release | |
| 16.04 LTS xenial | Not in release | |
| 14.04 LTS trusty | Not in release |
Patch details
| Package | Patch details |
|---|---|
| qemu |
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score |
7.5 · High
|
| Attack vector | Local |
| Attack complexity | High |
| Privileges required | High |
| User interaction | None |
| Scope | Changed |
| Confidentiality | High |
| Integrity impact | High |
| Availability impact | High |
| Vector | CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H |
References
Related Ubuntu Security Notices (USN)
- USN-4725-1
- QEMU vulnerabilities
- 8 February 2021