HOMEVULNERABILITIESCVE-2021-3939
HIGH

CVE-2021-3939

CWE-590Published: November 17, 2021· Updated: Jun 17, 2026

7.8
CVSS v3.1

Official Description

Ubuntu-specific modifications to accountsservice (in patch file debian/patches/0010-set-language.patch) caused the fallback_locale variable, pointing to static storage, to be freed, in the user_change_language_authorized_cb function. This is reachable via the SetLanguage dbus function. This is fixed in versions 0.6.55-0ubuntu12~20.04.5, 0.6.55-0ubuntu13.3, 0.6.55-0ubuntu14.1.

NVD Source

Technical Analysis

CVE-2021-3939 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires low 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 7.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

Canonical2 product(s)
accountsserviceubuntu linux
Source: NVD CPE · 4 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
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Official Patches & Advisories

ADVISORYhttps://ubuntu.com/security/notices/USN-5149-1
ADVISORYhttps://ubuntu.com/security/notices/USN-5149-1

All References (6)

→
http://packetstormsecurity.com/files/172848/Ubuntu-accountsservice-Double-Free-Memory-Corruption.html
→
https://bugs.launchpad.net/ubuntu/+source/accountsservice/+bug/1950149Broken Link
→
https://ubuntu.com/security/notices/USN-5149-1Vendor Advisory
→
http://packetstormsecurity.com/files/172848/Ubuntu-accountsservice-Double-Free-Memory-Corruption.html
→
https://bugs.launchpad.net/ubuntu/+source/accountsservice/+bug/1950149Broken Link
→
https://ubuntu.com/security/notices/USN-5149-1Vendor Advisory

Quick Facts

CVE IDCVE-2021-3939
CVSS Score7.8 / 10
SeverityHIGH
WeaknessCWE-590
CISA KEVNo
Affected1 vendor(s)
PublishedNov 17, 2021

Related CVEs (CWE-590)

CVE-2020-6016
9.8
CVE-2021-42377
9.8
CVE-2022-31627
9.8
CVE-2025-32911
9.0
CVE-2022-31625
8.1
CVE-2025-54899
7.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-3939 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.
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