CVE-2021-20181

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-05-13 · updated 2026-06-17
Weakness: CWE-367

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.

Affected products

Debian Linux: 9.0, 10.0
QEMU: through 5.2.0

References

https://bugzilla.redhat.com/show_bug.cgi?id=1927007
https://lists.debian.org/debian-lts-announce/2021/02/msg00024.html
https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
https://security.netapp.com/advisory/ntap-20210720-0009/
https://www.zerodayinitiative.com/advisories/ZDI-21-159/
https://bugzilla.redhat.com/show_bug.cgi?id=1927007
https://lists.debian.org/debian-lts-announce/2021/02/msg00024.html
https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
https://security.netapp.com/advisory/ntap-20210720-0009/
https://www.zerodayinitiative.com/advisories/ZDI-21-159/

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