What’s Vulnerable › Vulnerabilities
CVE-2021-20247
- Severity: high (CVSS 7.4 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 1.9% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2021-02-23 · updated 2026-06-17
- Weakness: CWE-20
Description
A flaw was found in mbsync before v1.3.5 and v1.4.1. Validations of the mailbox names returned by IMAP LIST/LSUB do not occur allowing a malicious or compromised server to use specially crafted mailbox names containing '..' path components to access data outside the designated mailbox on the opposite end of the synchronization channel. The highest threat from this vulnerability is to data confidentiality and integrity.
Affected products
- Debian Linux: 9.0
- Fedoraproject Extra Packages For Enterprise Linux: 8.0
- Fedoraproject Fedora: 32, 33
- Mbsync Project Mbsync: before 1.3.5; from 1.4.0 before 1.4.1 — fixed in 1.3.5, 1.4.1
How to fix
Upgrade to a fixed version: Mbsync Project Mbsync 1.3.5, 1.4.1. Check the vendor advisory for mitigations.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1928963
- https://lists.debian.org/debian-lts-announce/2022/07/msg00001.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CAXQLCK35QGRCRENRTGKJO4VVZGUXUJJ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GVDEBZQJMWDW5JFK4NTHH6DAFNAZTESW/
- https://security.gentoo.org/glsa/202208-15
- https://www.openwall.com/lists/oss-security/2021/02/22/1
- https://bugzilla.redhat.com/show_bug.cgi?id=1928963
- https://lists.debian.org/debian-lts-announce/2022/07/msg00001.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CAXQLCK35QGRCRENRTGKJO4VVZGUXUJJ/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GVDEBZQJMWDW5JFK4NTHH6DAFNAZTESW/
- https://security.gentoo.org/glsa/202208-15
- https://www.openwall.com/lists/oss-security/2021/02/22/1
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