CVE-2026-40019

Severity: medium (CVSS 5.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-28 · updated 2026-09-03
Weakness: CWE-400

Description

An unauthenticated attacker can send a truncated quoted argument to the ManageSieve login process, which makes it spin in an infinite loop consuming CPU. This can cause degradation or denial of service for Sieve script management, and repeated connections can consume all available CPU on the server. Monitor system for abnormal CPU usage and kill the offending process. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.

Affected products

Open-Xchange GmbH OX Dovecot CE: from 2.4.3 before 2.4.5 — fixed in 2.4.5

How to fix

Upgrade to a fixed version: Open-Xchange GmbH OX Dovecot CE 2.4.5. Check the vendor advisory for mitigations.

References

https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.json

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