CVE-2021-3578

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-02-16 · updated 2026-06-17
Weakness: CWE-704

Description

A flaw was found in mbsync before v1.3.6 and v1.4.2, where an unchecked pointer cast allows a malicious or compromised server to write an arbitrary integer value past the end of a heap-allocated structure by issuing an unexpected APPENDUID response. This could be plausibly exploited for remote code execution on the client.

Affected products

Debian Linux: 9.0
Fedoraproject Fedora: 33, 34
Isync Project Isync: before 1.3.6; 1.4.0, 1.4.1 — fixed in 1.3.6

How to fix

Upgrade to a fixed version: Isync Project Isync 1.3.6. Check the vendor advisory for mitigations.

References

http://www.openwall.com/lists/oss-security/2021/06/07/1
https://bugzilla.redhat.com/show_bug.cgi?id=1961710
https://bugzilla.redhat.com/show_bug.cgi?id=1967397
https://github.blog/2021-06-10-privilege-escalation-polkit-root-on-linux-with-bug/
https://lists.debian.org/debian-lts-announce/2022/07/msg00001.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RPIDLIJKNRJHUVBCL7QGAPAAVPIHQGXK/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U75UFEWRAZYKVL5NHMPBUOLWN3WXTOEI/
https://security.gentoo.org/glsa/202208-15
https://www.openwall.com/lists/oss-security/2021/06/07/1
http://www.openwall.com/lists/oss-security/2021/06/07/1
https://bugzilla.redhat.com/show_bug.cgi?id=1961710
https://bugzilla.redhat.com/show_bug.cgi?id=1967397

Get alerted when CVE-2021-3578 or the next vulnerability affects your stack