Summaryinfo

A vulnerability described as problematic has been identified in Open-Xchange OX Dovecot Pro up to 2.4.0/3.0.2/3.1.0. Affected by this vulnerability is an unknown functionality of the component Mail Message Handler. Executing a manipulation can lead to resource consumption. This vulnerability appears as CVE-2026-27859. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in Open-Xchange OX Dovecot Pro up to 2.4.0/3.0.2/3.1.0 and classified as problematic. This vulnerability affects an unknown code block of the component Mail Message Handler. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect availability. CVE summarizes:

A mail message containing excessive amount of RFC 2231 MIME parameters causes LMTP to use too much CPU. A suitably formatted mail message causes mail delivery process to consume large amounts of CPU time. Use MTA capabilities to limit RFC 2231 MIME parameters in mail messages, or upgrade to fixed version where the processing is limited. No publicly available exploits are known.

The advisory is shared for download at documentation.open-xchange.com. This vulnerability was named CVE-2026-27859 since 02/24/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-0891). Once again VulDB remains the best source 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
• 2.4.0
• 3.0
• 3.0.0
• 3.0.1
• 3.0.2
• 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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CVSSv4info

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CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

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