CVE-2026-27855 | Open-Xchange OX Dovecot Pro up to 2.3.0 SCRAM Protocol authentication replay (adv-2026-0001)

VDB-353853 · CVE-2026-27855 · ADV-2026-0001 OPEN-XCHANGE OX DOVECOT PRO UP TO 2.3.0 SCRAM PROTOCOL AUTHENTICATION REPLAY HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 5.9 $0-$5k 1.80+ Summaryinfo A vulnerability has been found in Open-Xchange OX Dovecot Pro up to 2.3.0 and classified as critical. Impacted is an unknown function of the component SCRAM Protocol Handler. Performing a manipulation results in authentication replay. This vulnerability was named CVE-2026-27855. The attack may be initiated remotely. There is no available exploit. Detailsinfo A vulnerability classified as critical has been found in Open-Xchange OX Dovecot Pro up to 2.3.0. This affects an unknown part of the component SCRAM Protocol Handler. The manipulation with an unknown input leads to a authentication replay vulnerability. CWE is classifying the issue as CWE-294. A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is: Dovecot OTP authentication is vulnerable to replay attack under specific conditions. If auth cache is enabled, and username is altered in passdb, then OTP credentials can be cached so that same OTP reply is valid. An attacker able to observe an OTP exchange is able to log in as the user. If authentication happens over unsecure connection, switch to SCRAM protocol. Alternatively ensure the communcations are secured, and if possible switch to OAUTH2 or SCRAM. No publicly available exploits are known. The advisory is shared at documentation.open-xchange.com. This vulnerability is uniquely identified as CVE-2026-27855 since 02/24/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 03/27/2026). MITRE ATT&CK project uses the attack technique T1040 for this issue. There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product. 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: 5.9 VulDB Meta Temp Score: 5.9 VulDB Base Score: 5.0 VulDB Temp Score: 5.0 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 6.8 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: Authentication replay CWE: CWE-294 / 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: no mitigation known 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-2026-27855 (🔒) GCVE (CVE): GCVE-0-2026-27855 GCVE (VulDB): GCVE-100-353853 Entryinfo Created: 03/27/2026 09:53 Changes: 03/27/2026 09:53 (63) Complete: 🔍 Cache ID: 99:FC4:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸