CVE-2026-61909: CWE-420 Unprotected Alternate Channel in cyrusimap Cyrus IMAP
CVE-2026-61909 is a vulnerability in Cyrus IMAP before version 3.12.4 where CalDAV/CardDAV multiget requests bypass per-href access controls. An authenticated DAV user with some shared access to another user's calendar or address book can read unshared events or contacts by crafting specific multiget REPORT requests.
AI Analysis
Technical Summary
This vulnerability involves an unprotected alternate channel (CWE-420) in Cyrus IMAP's CalDAV/CardDAV implementation. Specifically, the multiget REPORT method bypasses per-href ACL checks, allowing an authenticated user with limited shared access to read data that should be inaccessible, such as unshared calendar events or contacts. The issue affects versions 3.9.0 and 3.11.0, and was fixed in versions after 3.12.4.
Potential Impact
The vulnerability allows unauthorized read access to calendar or address book data that is not shared with the attacker, violating confidentiality. There is no impact on integrity or availability. The CVSS score is 3.5 (low severity), reflecting limited impact and the requirement for authenticated access with some shared privileges.
Mitigation Recommendations
No official patch or remediation level is provided in the available data. Users should upgrade to Cyrus IMAP version 3.12.4 or later where this issue is fixed. Until then, restrict authenticated DAV user access carefully and monitor for suspicious multiget REPORT requests. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
CVE-2026-61909: CWE-420 Unprotected Alternate Channel in cyrusimap Cyrus IMAP
Description
CVE-2026-61909 is a vulnerability in Cyrus IMAP before version 3.12.4 where CalDAV/CardDAV multiget requests bypass per-href access controls. An authenticated DAV user with some shared access to another user's calendar or address book can read unshared events or contacts by crafting specific multiget REPORT requests.
CVSS v3.1
Score 3.5low
Affected software
pkg:github/cyrusimap/cyrus-imapRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability involves an unprotected alternate channel (CWE-420) in Cyrus IMAP's CalDAV/CardDAV implementation. Specifically, the multiget REPORT method bypasses per-href ACL checks, allowing an authenticated user with limited shared access to read data that should be inaccessible, such as unshared calendar events or contacts. The issue affects versions 3.9.0 and 3.11.0, and was fixed in versions after 3.12.4.
Potential Impact
The vulnerability allows unauthorized read access to calendar or address book data that is not shared with the attacker, violating confidentiality. There is no impact on integrity or availability. The CVSS score is 3.5 (low severity), reflecting limited impact and the requirement for authenticated access with some shared privileges.
Mitigation Recommendations
No official patch or remediation level is provided in the available data. Users should upgrade to Cyrus IMAP version 3.12.4 or later where this issue is fixed. Until then, restrict authenticated DAV user access carefully and monitor for suspicious multiget REPORT requests. Patch status is not yet confirmed — check the vendor advisory for current remediation guidance.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mitre
- Date Reserved
- 2026-07-13T00:00:00.000Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6aa28ec9acd9273b4901d487
Added to database: 09/10/2026, 11:04:41 UTC
Last enriched: 09/10/2026, 11:07:10 UTC
Last updated: 09/10/2026, 11:12:05 UTC
Views: 4
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