CVE-2021-20181
A race condition flaw was found in the 9pfs server implementation of QEMU up to and including 5.2.0.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.33%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H
- EPSS
- 0.33% probability · 26th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-367, CWE-362
- Affected
- qemu/qemu · debian/debian linux
- Source
- secalert@redhat.com
EPSS 0.3% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1927007Issue Tracking, Patch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/02/msg00024.htmlMailing List, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2022/09/msg00008.htmlMailing List, Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210720-0009/Third Party Advisory
- https://www.zerodayinitiative.com/advisories/ZDI-21-159/Third Party Advisory, VDB Entry
- https://bugzilla.redhat.com/show_bug.cgi?id=1927007Issue Tracking, Patch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/02/msg00024.htmlMailing List, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2022/09/msg00008.htmlMailing List, Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210720-0009/Third Party Advisory
- https://www.zerodayinitiative.com/advisories/ZDI-21-159/Third Party Advisory, VDB Entry
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.