HOMEVULNERABILITIESCVE-2021-20181
HIGH

CVE-2021-20181

CWE-367Published: May 13, 2021· Updated: Jun 17, 2026

7.5
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-20181 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires high privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 7.5.

The vulnerability has a "Changed" scope, meaning successful exploitation can impact components beyond the vulnerable component itself — such as the host operating system or adjacent services.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityHigh
Privileges Req.High
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

Affected Vendors & Products

Debian1 product(s)
debian linux
qemu1 product(s)
qemu
Source: NVD CPE · 3 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
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Official Patches & Advisories

All References (10)

Quick Facts

CVE IDCVE-2021-20181
CVSS Score7.5 / 10
SeverityHIGH
WeaknessCWE-367
CISA KEVNo
Affected2 vendor(s)
PublishedMay 13, 2021

Related CVEs (CWE-367)

Recommended Actions

  • Apply vendor patches immediately
  • Monitor CVE-2021-20181 in threat intel feeds
  • Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.