CVE-2026-27855

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Summary

CVECVE-2026-27855
StatePUBLISHED
AssignerOX
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-27 09:16:19 UTC
Updated2026-04-29 19:23:00 UTC
DescriptionDovecot 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.

Risk And Classification

Primary CVSS: v3.1 5.9 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS: 0.000170000 probability, percentile 0.040870000 (date 2026-05-05)

Problem Types: CWE-294 | CWE-294 Authentication Bypass by Capture-replay

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary5.9MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
3.1[email protected]Secondary6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
3.1CNACVSS6.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Dovecot Dovecot All All All All
Application Open-xchange Dovecot All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Open-Xchange GmbH OX Dovecot Pro affected 2.3.0 semver Not specified

References

ReferenceSourceLinkTags
documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json [email protected] documentation.open-xchange.com Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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