CVE-2021-3939 | Free of static data in accountsservice

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.

Published: 2021-11-16 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3939 is rated Moderate Risk (40.4/100): CVSS High severity, with low exploitation likelihood (EPSS 0.34%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-3939

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.12% 0.34% +0.22%
2 2026-01-10 0.17% 0.12% -0.05%
3 2025-12-16 — 0.17% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3939

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.1 6.0 [email protected]
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
7.2 2.0 HIGH
AV:L/AC:L/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:L)
Requires local access to the target system.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 3.9 10.0 [email protected]

Weakness enumeration for CVE-2021-3939

OS Trackers for CVE-2021-3939

vendor priority summary link
debian unimportant CVE-2021-3939 unimportant priority: Debian including 1 source packages (accountsservice), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-3939
ubuntu high CVE-2021-3939 high priority: Ubuntu including 1 source packages (accountsservice), 8 status rows across 8 suites (bionic, focal, hirsute, impish, jammy, trusty, upstream, xenial): released 4, not-affected 3, needs-triage 1. https://ubuntu.com/security/CVE-2021-3939

Affected software / configurations for CVE-2021-3939

Vendor Product Version Raw CPE
canonical accountsservice >= 0.6.55-0ubuntu12\~20.04, < 0.6.55-0ubuntu12\~20.05 cpe:2.3:a:canonical:accountsservice:*:*:*:*:*:*:*:*
canonical accountsservice >= 0.6.55-0ubuntu13, < 0.6.55-0ubuntu13.3 cpe:2.3:a:canonical:accountsservice:*:*:*:*:*:*:*:*
canonical accountsservice >= 0.6.55-0ubuntu14, < 0.6.55-0ubuntu14.1 cpe:2.3:a:canonical:accountsservice:*:*:*:*:*:*:*:*
canonical ubuntu_linux 20.04 cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 21.04 cpe:2.3:o:canonical:ubuntu_linux:21.04:*:*:*:*:*:*:*
canonical ubuntu_linux 21.10 cpe:2.3:o:canonical:ubuntu_linux:21.10:*:*:*:*:*:*:*

References for CVE-2021-3939

cvelogic Threat Intelligence