CVE-2026-61909

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-09 · updated 2026-09-16
Weakness: CWE-420

Description

An issue was discovered in Cyrus IMAP before 3.12.4. CalDAV/CardDAV multiget bypasses a per-href ACL. An authenticated DAV user with some shared access to another user's calendar or address book could read even unshared events or contacts by including the target hrefs in a calendar-multiget or addressbook-multiget REPORT.

Affected products

cyrusimap Cyrus IMAP: before 3.8.8; from 3.9.0 before 3.10.4; from 3.11.0 before 3.12.4 — fixed in 3.10.4, 3.12.4, 3.8.8

How to fix

Upgrade to a fixed version: cyrusimap Cyrus IMAP 3.10.4, 3.12.4, 3.8.8. Check the vendor advisory for mitigations.

References

https://cyrusimap.org
https://www.cyrusimap.org/3.12/imap/download/release-notes/3.10/x/3.10.4.html
https://www.cyrusimap.org/3.12/imap/download/release-notes/3.12/x/3.12.4.html
https://www.cyrusimap.org/3.12/imap/download/release-notes/3.8/x/3.8.8.html

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