CVE-2026-33605

Severity: high (CVSS 7.5 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 crash the ManageSieve login process by sending a small malformed command before authenticating. If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management. 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 2.3.0 before 2.4.5 — fixed in 2.4.5
Open-Xchange GmbH OX Dovecot Pro: from 2.3.0 before 2.3.22.2; from 3.0.0 before 3.0.7; from 3.1.0 before 3.1.6 — fixed in 2.3.22.2, 3.0.7, 3.1.6

How to fix

Upgrade to a fixed version: Open-Xchange GmbH OX Dovecot CE 2.4.5; Open-Xchange GmbH OX Dovecot Pro 2.3.22.2, 3.0.7, 3.1.6. 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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