Summaryinfo

A vulnerability marked as problematic has been reported in Open-Xchange OX Dovecot Pro up to 2.3.0/2.4.0/3.1.0. Affected is an unknown function of the component Message Handler. Performing a manipulation results in resource consumption. This vulnerability is reported as CVE-2026-27858. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Open-Xchange OX Dovecot Pro up to 2.3.0/2.4.0/3.1.0. This affects an unknown code of the component Message Handler. The manipulation with an unknown input leads to a resource consumption vulnerability. CWE is classifying the issue as CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. This is going to have an impact on availability. The summary by CVE is:

Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. No publicly available exploits are known.

It is possible to read the advisory at documentation.open-xchange.com. This vulnerability is uniquely identified as CVE-2026-27858 since 02/24/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

The vulnerability scanner Nessus provides a plugin with the ID 304117 (Linux Distros Unpatched Vulnerability : CVE-2026-27858), which helps to determine the existence of the flaw in a target environment.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (304117) and CERT Bund (WID-SEC-2026-0891). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• Open Source Dovecot

Productinfo

Type

• Mail Server Software

Vendor

• Open-Xchange

Name

• OX Dovecot Pro

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.3.0
• 2.4.0
• 3.0
• 3.1.0

License

• open-source

Website

• Vendor: https://www.open-xchange.com/

CPE 2.3info

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CPE 2.2info

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