CVE-2021-20181

mediumpriority · track · 30EPSS 0.003 · 26 %ileDEEURUUS

grimoire priorityP3 · Track

Exploitable?

—

no known exploitation

Likely / severe?

0.33% (26th) EPSS

CVSS 6.9 · medium

Is it mine?

19 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-27

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

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 6.9–7.5

v2.06.9mediumAV:L/AC:M/Au:N/C:C/I:C/A:Cprimary · NVD / NIST USexploitability 3.4 · impact 10

v3.17.5highCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 0.8 · impact 6

v3.17.5highAV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.16.9mediumCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-362USprimaryCWE-367USCWE-416US

affected products (19)

Products and version ranges known to be affected.

Debian Linuxall versionscert_bundDEcpe:/o:debian:debian_linux:-
Open Source QEMU <5.0.0-rc3all versionscert_bundDE
Oracle Linuxall versionscert_bundDEcpe:/o:oracle:linux:-
SUSE Linuxall versionscert_bundDEcpe:/o:suse:suse_linux:-
Ubuntu Linuxall versionscert_bundDEcpe:/o:canonical:ubuntu_linux:-
Open Source QEMU< 5.0.0-rc3cert_bundDE
n/a qemu≤ up to, including 5.2.0enisa_euvdEU
Fabrice Bellard QEMU≤ 5.2.0fstec_bduRU
АО «Концерн ВНИИНС» ОС ОН «Стрелец»≤ 16.01.2023fstec_bduRU
АО «НППКТ» ОСОН ОСнова Оnyx≤ 2.5fstec_bduRU
ООО «РусБИТех-Астра» Astra Linux Special Edition≤ 1.7fstec_bduRU
ООО «РусБИТех-Астра» Astra Linux Special Edition≤ 4.7fstec_bduRU
ООО «РусБИТех-Астра» Astra Linux Special Edition≤ 1.6 «Смоленск»fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 8fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 10fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 9fstec_bduRU
debian debian linux= 10.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
debian debian linux= 9.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
qemu qemu≤ 5.2.0nvdUScpe:2.3:a:qemu:qemu:*:*:*:*:*:*:*:*

advisories (1)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2022-1279QEMU: Schwachstelle ermöglicht PrivilegieneskalationDeutsch2021-02-10csaf · cert_bundDE
Ein lokaler Angreifer kann eine Schwachstelle in QEMU ausnutzen, um seine Privilegien zu erhöhen.

also known as (4)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cert_bund nvd NVD CVE.org MITRE

published 2021-05-13modified 2026-06-17

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+4134 more

references (25)

External citations — patches, advisories, analysis.

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