CVE-2021-44143

Name: CVE-2021-44143
Creator: NVD / NIST
Published: 2021-11-22T20:15:18.223+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 3.66%

Last modified Jun 17, 2026

CVE-2021-44143 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. A flaw was found in mbsync in isync 1.4.0 through 1.4.3. Due to an unchecked condition, a malicious or compromised IMAP server could use a crafted mail message that lacks headers (i.e., one that starts with an empty line) to provoke a heap overflow, which could conceivably be exploited for remote code execution.. EPSS estimates a 3.66% chance of exploitation in the next 30 days.

Description

A flaw was found in mbsync in isync 1.4.0 through 1.4.3. Due to an unchecked condition, a malicious or compromised IMAP server could use a crafted mail message that lacks headers (i.e., one that starts with an empty line) to provoke a heap overflow, which could conceivably be exploited for remote code execution.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

3.66%

88.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Isync Project	Isync	>= 1.4.0, <= 1.4.3
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0
Debian	Debian Linux	11.0
Fedoraproject	Fedora	34
Fedoraproject	Fedora	35

References

http://www.openwall.com/lists/oss-security/2021/12/03/2Mailing List
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=999804Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CYZ2GNB4ZO2T27D2XNUWMCS3THZYSJQU/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCBSY7OZ57XNC6ZYXF6WU5KBSWITZVDX/
https://security.gentoo.org/glsa/202208-15Third Party Advisory
https://sourceforge.net/p/isync/isync/commit_browserPatch, Third Party Advisory
https://sourceforge.net/p/isync/isync/ref/master/tags/Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/12/03/2Mailing List
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=999804Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CYZ2GNB4ZO2T27D2XNUWMCS3THZYSJQU/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCBSY7OZ57XNC6ZYXF6WU5KBSWITZVDX/
https://security.gentoo.org/glsa/202208-15Third Party Advisory
https://sourceforge.net/p/isync/isync/commit_browserPatch, Third Party Advisory
https://sourceforge.net/p/isync/isync/ref/master/tags/Third Party Advisory

Timeline

Published: Nov 22, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-44143?

How severe is CVE-2021-44143?

CVE-2021-44143 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 3.66% probability of exploitation in the next 30 days.

How do I fix CVE-2021-44143?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-44143?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST