CVE-2026-61911: CWE-497 Exposure of Sensitive System Information to an Unauthorized Control Sphere in cyrusimap Cyrus IMAP
CVE-2026-61911 is a medium severity vulnerability in Cyrus IMAP before version 3.12.4. It allows an authenticated user to probe the existence of other users' private mailboxes or read shared mailbox annotations by exploiting a Sieve mailbox existence oracle during LMTP delivery. This exposure of sensitive system information could lead to unauthorized knowledge about mailbox presence or annotation values.
AI Analysis
Technical Summary
This vulnerability in Cyrus IMAP versions prior to 3.12.4 involves a Sieve mailbox existence oracle. An authenticated attacker can install a Sieve script that detects whether another user's private mailbox exists or reads shared mailbox annotations by observing which fileinto branch is triggered during LMTP delivery. This behavior leaks sensitive system information to unauthorized users, classified under CWE-497 (Exposure of Sensitive System Information to an Unauthorized Control Sphere).
Potential Impact
The vulnerability allows an authenticated user to gain information about the existence of other users' private mailboxes and the values of shared mailbox annotations. This information disclosure does not affect confidentiality of mailbox contents directly but leaks metadata that could be used for further reconnaissance or targeted attacks. There is no impact on integrity or availability.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level is provided, users should monitor the vendor's updates for a patch addressing this issue. Until a patch is available, restrict authenticated user permissions to limit the ability to install arbitrary Sieve scripts if possible.
CVE-2026-61911: CWE-497 Exposure of Sensitive System Information to an Unauthorized Control Sphere in cyrusimap Cyrus IMAP
Description
CVE-2026-61911 is a medium severity vulnerability in Cyrus IMAP before version 3.12.4. It allows an authenticated user to probe the existence of other users' private mailboxes or read shared mailbox annotations by exploiting a Sieve mailbox existence oracle during LMTP delivery. This exposure of sensitive system information could lead to unauthorized knowledge about mailbox presence or annotation values.
CVSS v3.1
Score 4.3medium
Affected software
pkg:github/cyrusimap/cyrus-imapdRun 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 in Cyrus IMAP versions prior to 3.12.4 involves a Sieve mailbox existence oracle. An authenticated attacker can install a Sieve script that detects whether another user's private mailbox exists or reads shared mailbox annotations by observing which fileinto branch is triggered during LMTP delivery. This behavior leaks sensitive system information to unauthorized users, classified under CWE-497 (Exposure of Sensitive System Information to an Unauthorized Control Sphere).
Potential Impact
The vulnerability allows an authenticated user to gain information about the existence of other users' private mailboxes and the values of shared mailbox annotations. This information disclosure does not affect confidentiality of mailbox contents directly but leaks metadata that could be used for further reconnaissance or targeted attacks. There is no impact on integrity or availability.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level is provided, users should monitor the vendor's updates for a patch addressing this issue. Until a patch is available, restrict authenticated user permissions to limit the ability to install arbitrary Sieve scripts if possible.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mitre
- Date Reserved
- 2026-07-13T00:00:00.000Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6aa1bca9acd9273b49cd3c6d
Added to database: 09/09/2026, 20:08:09 UTC
Last enriched: 09/09/2026, 20:23:08 UTC
Last updated: 09/09/2026, 23:45:00 UTC
Views: 6
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