CVE-2026-27855

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.

CVSS v3 6.8 MEDIUM

6.8^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 1.6 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction REQUIRED

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json	Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:dovecot:dovecot::::::::
	cpe:2.3:a:open-xchange:dovecot:::::pro:::*

History

26 Oct 2026, 22:10

Type	Values Removed	Values Added
Summary		(es) La autenticación OTP de Dovecot es vulnerable a ataques de repetición bajo condiciones específicas. Si la caché de autenticación está habilitada y el nombre de usuario se altera en passdb, entonces las credenciales OTP pueden ser almacenadas en caché de modo que la misma respuesta OTP sea válida. Un atacante capaz de observar un intercambio OTP puede iniciar sesión como el usuario. Si la autenticación ocurre a través de una conexión no segura, cambie al protocolo SCRAM. Alternativamente, asegure que las comunicaciones estén protegidas y, si es posible, cambie a OAUTH2 o SCRAM. No se conocen exploits disponibles públicamente.

Information

Published : 2026-03-27 09:16

Updated : 2026-10-26 22:10

NVD link : CVE-2026-27855

Mitre link : CVE-2026-27855

CVE.ORG link : CVE-2026-27855

JSON object : View

Products Affected

open-xchange

dovecot

dovecot

dovecot

CWE

CWE-294

Authentication Bypass by Capture-replay

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