CVE-2021-20181
qemu-system-mips: A race condition flaw was found in the 9pfs server implementation of QEMUup to and including 5.2.0
CVE-2021-20181 is fixed in 25 products on 1 platform, first by qemu 1:2.11+dfsg-1ubuntu7.35, released January 31, 2021. It is not reported as exploited. Patch Radar priority: Routine.
Routine
CVSS
n/a
Medium
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0033
26th percentile
A race condition flaw was found in the 9pfs server implementation of QEMUup to and including 5.2.0. This flaw allows a malicious 9p client to causea use-after-free error, potentially escalating their privileges on thesystem. The highest threat from this vulnerability is to confidentiality,integrity as well as system availability.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| qemu · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-block-extra · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-block-extra 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-block-extra · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-block-extra 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-block-extra · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-block-extra 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-block-extra · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-block-extra 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-block-supplemental · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-block-supplemental 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-block-supplemental · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-block-supplemental 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-guest-agent · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-guest-agent 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-guest-agent · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-guest-agent 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-guest-agent · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-guest-agent 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-guest-agent · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-guest-agent 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-kvm · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-kvm 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-kvm · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-kvm 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-arm · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-arm 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-arm · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-arm 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-arm · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-arm 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-arm · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-arm 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-common · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-common 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-common · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-common 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-common · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-common 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-common · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-common 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-data · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-data 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-data · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-data 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-data · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-data 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-gui · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-gui 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-gui · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-gui 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-gui · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-gui 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-mips · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-mips 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-mips · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-mips 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-mips · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-mips 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-mips · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-mips 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-misc · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-misc 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-misc · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-misc 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-misc · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-misc 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-misc · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-misc 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-modules-opengl · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-modules-opengl 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-modules-opengl · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-modules-opengl 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-modules-spice · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-modules-spice 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-modules-spice · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-modules-spice 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-ppc · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-ppc 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-ppc · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-ppc 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-ppc · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-ppc 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-ppc · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-ppc 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-s390x · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-s390x 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-s390x · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-s390x 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-s390x · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-s390x 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-s390x · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-s390x 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-sparc · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-sparc 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-sparc · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-sparc 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-sparc · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-sparc 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-sparc · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-sparc 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-x86 · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-system-x86 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-system-x86 · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-x86 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-x86 · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-x86 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-x86 · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-x86 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-x86-microvm · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-x86-microvm 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-x86-xen · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-system-x86-xen 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-system-x86-xen · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-x86-xen 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-x86-xen · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-x86-xen 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-xen · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-system-xen 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-system-xen · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-system-xen 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-user · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-user 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-user · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-user 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-user · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-user 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-user · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-user 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-user-binfmt · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-user-binfmt 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-user-binfmt · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-user-binfmt 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-user-binfmt · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-user-binfmt 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-user-binfmt · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-user-binfmt 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-user-static · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-user-static 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-user-static · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-user-static 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-user-static · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-user-static 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-user-static · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-user-static 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-utils · Ubuntu 18.04.6 LTS (bionic) | 1:2.11+dfsg-1ubuntu7.35 | qemu-utils 1:2.11+dfsg-1ubuntu7.35 | Jan 31, 2021 |
| qemu-utils · Ubuntu 20.04 LTS (focal) | 1:4.2-3ubuntu6.12 | qemu-utils 1:4.2-3ubuntu6.12 | Jan 31, 2021 |
| qemu-utils · Ubuntu 24.10 (oracular) | 1:5.2+dfsg-6ubuntu2 | qemu-utils 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
| qemu-utils · Ubuntu 25.04 (plucky) | 1:5.2+dfsg-6ubuntu2 | qemu-utils 1:5.2+dfsg-6ubuntu2 | Jan 16, 2026 |
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