CVE-2026-40016: Medium severity Dovecot Pigeonhole (Sieve) vulnerability
Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130 times of the configured limit. Attacker can use this to degrade server performance and bypass configured CPU time limits for Sieve scripts. Install fixed version, or alternatively prevent direct access to Sieve scripts via ManageSieve or local access. No publicly available exploits are known.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-40016?
CVE-2026-40016 is considered a high-severity vulnerability as it allows attackers to significantly degrade server performance.
How do I fix CVE-2026-40016?
To fix CVE-2026-40016, upgrade to the latest fixed version of Dovecot Pigeonhole (Sieve) provided by the vendor.
What type of attack is associated with CVE-2026-40016?
CVE-2026-40016 exploits the ManageSieve service to upload malicious scripts that can bypass CPU time limits.
What are the consequences of CVE-2026-40016?
The consequences of CVE-2026-40016 include degraded performance of the mail server due to unregulated CPU usage by Sieve scripts.
Which software is affected by CVE-2026-40016?
CVE-2026-40016 affects Dovecot Pigeonhole (Sieve) software specifically.