CVE-2026-27856 | Open-Xchange OX Dovecot Pro up to 2.3.0 Doveadm Http Service improper authentication (adv-2026-0001)

VDB-353844 · CVE-2026-27856 · ADV-2026-0001 OPEN-XCHANGE OX DOVECOT PRO UP TO 2.3.0 DOVEADM HTTP SERVICE IMPROPER AUTHENTICATION HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 6.4 $0-$5k 1.80+ Summaryinfo A vulnerability categorized as critical has been discovered in Open-Xchange OX Dovecot Pro up to 2.3.0. The impacted element is an unknown function of the component Doveadm Http Service. The manipulation results in improper authentication. This vulnerability is cataloged as CVE-2026-27856. The attack may be launched remotely. There is no exploit available. It is advisable to upgrade the affected component. Detailsinfo A vulnerability classified as critical has been found in Open-Xchange OX Dovecot Pro up to 2.3.0. Affected is an unknown functionality of the component Doveadm Http Service. The manipulation with an unknown input leads to a improper authentication vulnerability. CWE is classifying the issue as CWE-287. When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes: Doveadm credentials are verified using direct comparison which is susceptible to timing oracle attack. An attacker can use this to determine the configured credentials. Figuring out the credential will lead into full access to the affected component. Limit access to the doveadm http service port, install fixed version. No publicly available exploits are known. The advisory is shared for download at documentation.open-xchange.com. This vulnerability is traded as CVE-2026-27856 since 02/24/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available. Upgrading eliminates this vulnerability. Productinfo Type Mail Server Software Vendor Open-Xchange Name OX Dovecot Pro Version 2.0 2.1 2.2 2.3.0 License open-source Website Vendor: https://www.open-xchange.com/ CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 6.5 VulDB Meta Temp Score: 6.4 VulDB Base Score: 5.6 VulDB Temp Score: 5.4 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 7.4 CNA Vector: 🔒 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Improper authentication CWE: CWE-287 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Timelineinfo 02/24/2026 CVE reserved 03/27/2026 +31 days Advisory disclosed 03/27/2026 +0 days VulDB entry created 03/27/2026 +0 days VulDB entry last update Sourcesinfo Vendor: open-xchange.com Advisory: adv-2026-0001 Status: Confirmed CVE: CVE-2026-27856 (🔒) GCVE (CVE): GCVE-0-2026-27856 GCVE (VulDB): GCVE-100-353844 Entryinfo Created: 03/27/2026 09:51 Changes: 03/27/2026 09:51 (64) Complete: 🔍 Cache ID: 99:C00:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸