Is CVE-2021-20181 in the CISA KEV catalog?

No. CVE-2021-20181 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-20181?

CVE-2021-20181 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-20181?

CVE-2021-20181 has an EPSS score of 0.32% (24th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-20181?

Upgrade qemu on debian 11 to 1:5.2+dfsg-4 or later. Fixes are available for 25 affected products.

CVE & CISA-KEV Catalog

CVE-2021-20181

HIGH

7.5

CVSS v3

NVD

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.

CWE-367TOCTOU Race Condition CWE-362Race Condition

How to fix

Remediation Available

qemuDebian

Fixed in:1:5.2+dfsg-4CVE-2021-20181

qemuUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

qemu-block-extraUbuntu

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-commonUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

qemu-guest-agentUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-keymapsUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

qemu-kvmUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-systemUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-aarch64Ubuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

qemu-system-armUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-commonUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-dataUbuntu

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-guiUbuntu

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-mipsUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

qemu-system-miscUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-ppcUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-s390xUbuntu

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-sparcUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-x86Ubuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.49USN-4725-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.35USN-4725-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-x86-microvmUbuntu

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-system-x86-xenUbuntu

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

Fixed in:1:4.2-3ubuntu6.12USN-4725-1

qemu-userUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-user-binfmtUbuntu

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-user-staticUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

qemu-utilsUbuntu

Fixed in:2.0.0+dfsg-2ubuntu1.47+esm6USN-8412-1

Fixed in:1:2.5+dfsg-5ubuntu10.51+esm4USN-8412-1

Fixed in:1:2.11+dfsg-1ubuntu7.42+esm5USN-8412-1

Fixed in:1:4.2-3ubuntu6.30+esm1USN-8412-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityHigh

Privileges RequiredHigh

User InteractionNone

ScopeChanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:H

Exploit Intelligence

0.32%probability of exploitation in 30 days

24thpercentile

Low risk: more likely to be exploited than 24% of all known CVEs.

References

Patch1

bugzilla.redhat.com

Third-Party Advisory4

Related Vulnerabilities

Other CWE-367 (TOCTOU Race Condition) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2022-36980	High	8.1	83%	-	Fix
CVE-2024-30088	High	7.0	68%	KEV + Ransom	Fix
CVE-2004-0594	Medium	5.1	55%	-	Fix
CVE-2024-50379	Critical	9.8	44%	-	Fix
CVE-2023-38146	High	8.8	39%	-	Fix
CVE-2024-0132	Critical	9.0	37%	-	Fix

Embed a live status badge for CVE-2021-20181

Markdown

[![CVE-2021-20181](https://tridentstack.com/cve/badge/CVE-2021-20181.svg)](https://tridentstack.com/cve/CVE-2021-20181)

HTML

<a href="https://tridentstack.com/cve/CVE-2021-20181"><img src="https://tridentstack.com/cve/badge/CVE-2021-20181.svg" alt="CVE-2021-20181"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.