{"id":"CVE-2021-20181","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-20181","generatedAt":"2026-10-28T04:17:30.779Z","title":"A race condition flaw was found in the 9pfs server implementation of QEMU up to and including 5.2.0.","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.","published":"2021-05-13T16:15:08.000Z","lastModified":"2026-06-17T03:33:26.000Z","status":"Modified","sourceIdentifier":"secalert@redhat.com","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H"},"cwe":["CWE-367","CWE-362"],"affected":["qemu/qemu","debian/debian linux"],"epss":{"score":0.00333,"percentile":0.26337,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"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."},"changes":[],"references":[{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=1927007","tags":["Issue Tracking","Patch","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://lists.debian.org/debian-lts-announce/2021/02/msg00024.html","tags":["Mailing List","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html","tags":["Mailing List","Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://security.netapp.com/advisory/ntap-20210720-0009/","tags":["Third Party Advisory"],"source":"secalert@redhat.com"},{"url":"https://www.zerodayinitiative.com/advisories/ZDI-21-159/","tags":["Third Party Advisory","VDB Entry"],"source":"secalert@redhat.com"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=1927007","tags":["Issue Tracking","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2021/02/msg00024.html","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html","tags":["Mailing List","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://security.netapp.com/advisory/ntap-20210720-0009/","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://www.zerodayinitiative.com/advisories/ZDI-21-159/","tags":["Third Party Advisory","VDB Entry"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-20181","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}