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CVE-2021-44143

33
FAUCET Score

CVE-2021-44143 is a critical heap overflow vulnerability in mbsync (isync versions 1.4.0-1.4.3) that allows a malicious IMAP server to trigger remote code execution via a crafted, headerless email. With a CVSS score of 9.8, it presents a severe risk due to its network-based attack vector, low attack complexity, and high impact on confidentiality, integrity, and availability. While there is no evidence of active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has garnered significant community discussion with 10 mentions. Affected products include various Debian and Fedora distributions of isync.

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.4.0, <= 1.4.3CPE matchmatch criteria
cpe:2.3:a:isync_project:isync:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
11.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.66%
Probability of exploitation in next 30 days
EPSS Percentile
88.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0366 is in the 81st percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

bugs.debian.org / cgi-bin/bugreport.cgi
Third Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/CYZ2GNB4ZO2T27D2XNUWMCS3THZYSJQU
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/LCBSY7OZ57XNC6ZYXF6WU5KBSWITZVDX
security.gentoo.org / glsa/202208-15
Third Party Advisory
sourceforge.net / p/isync/isync/commit_browser
PatchThird Party Advisory
sourceforge.net / p/isync/isync/ref/master/tags
Third Party Advisory
openwall.com / lists/oss-security/2021/12/03/2
Mailing List