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Fencer Intel
critical 9.8

CVE-2021-44143 json

A flaw was found in mbsync in isync 1.4.0 through 1.4.3.

published 4y ago modified 4mo ago also EUVD-2021-30996

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.8%
EPSS 3.8% chance of exploitation in 30 days, percentile 90%
public exploits
0
none known

Summary

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.

Patch / fix

  • isync Debian 14, Debian 13, Debian 12 1.4.4-1

debian advisories DEBIAN-CVE-2021-44143

  • isync openSUSE Tumbleweed 1.4.4-1.1

opensuse advisories openSUSE-SU-2024:11779-1

  • isync Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 1.4.4-r0

alpine advisories ALPINE-CVE-2021-44143

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • isync Arch Linux 1.4.4-1

arch linux advisories AVG-2579

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-44143 updated cvss 9.8

isync: specially crafted mail message may cause heap overflow

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.78% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.