Denial of Service Vulnerability in ManageSieve by Open-Xchange

CVE-2026-40019

What is CVE-2026-40019?

A vulnerability exists in Open-Xchange's ManageSieve service allowing an unauthenticated attacker to exploit a truncated quoted argument during the login process. This exploitation can lead the service into an infinite loop, excessively consuming CPU resources. As a result, it may degrade service functionality or lead to a complete denial of service for Sieve script management. It is crucial for users to monitor system performance for abnormal CPU usage and restrict network access to the ManageSieve service to trusted clients. Users should also ensure that they update to the latest non-vulnerable version to mitigate any risks associated with this issue.

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