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DEBIAN-CVE-2026-27855

Type: advisorySource: OSV1 source record

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.

Announced Group revision 1
Original source ↗

DEBIAN-CVE-2026-27855

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:DEBIAN-CVE-2026-27855

dovecot

Source reference: /affected/0/package/name

Affected versions
1:2.3.19.1+dfsg1-2.1

Source reference: /affected/0/versions

1:2.3.19.1+dfsg1-2.1+deb12u1

Source reference: /affected/0/versions

Fixed versions
1:2.3.19.1+dfsg1-2.1+deb12u2

Source reference: /affected/0/ranges

Prerequisites
Not stated in this record

dovecot

Source reference: /affected/1/package/name

Affected versions
1:2.4.1+dfsg1-6

Source reference: /affected/1/versions

1:2.4.1+dfsg1-6+deb13u1

Source reference: /affected/1/versions

1:2.4.1+dfsg1-6+deb13u2

Source reference: /affected/1/versions

1:2.4.1+dfsg1-6+deb13u3

Source reference: /affected/1/versions

Fixed versions
1:2.4.1+dfsg1-6+deb13u4

Source reference: /affected/1/ranges

Prerequisites
Not stated in this record

dovecot

Source reference: /affected/2/package/name

Affected versions
1:2.4.1+dfsg1-6

Source reference: /affected/2/versions

1:2.4.1+dfsg1-7

Source reference: /affected/2/versions

1:2.4.1+dfsg1-8

Source reference: /affected/2/versions

1:2.4.1+dfsg1-9

Source reference: /affected/2/versions

1:2.4.2+dfsg1-1

Source reference: /affected/2/versions

1:2.4.2+dfsg1-2

Source reference: /affected/2/versions

1:2.4.2+dfsg1-3

Source reference: /affected/2/versions

1:2.4.2+dfsg1-4

Source reference: /affected/2/versions

Fixed versions
1:2.4.3+dfsg1-1

Source reference: /affected/2/ranges

Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "1:2.3.19.1+dfsg1-2.1+deb12u2"
          }
        ]
      }
    ],
    "package": {
      "name": "dovecot",
      "purl": "pkg:deb/debian/dovecot?arch=source&distro=bookworm",
      "ecosystem": "Debian:12"
    },
    "versions": [
      "1:2.3.19.1+dfsg1-2.1",
      "1:2.3.19.1+dfsg1-2.1+deb12u1"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27855.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "1:2.4.1+dfsg1-6+deb13u4"
          }
        ]
      }
    ],
    "package": {
      "name": "dovecot",
      "purl": "pkg:deb/debian/dovecot?arch=source&distro=trixie",
      "ecosystem": "Debian:13"
    },
    "versions": [
      "1:2.4.1+dfsg1-6",
      "1:2.4.1+dfsg1-6+deb13u1",
      "1:2.4.1+dfsg1-6+deb13u2",
      "1:2.4.1+dfsg1-6+deb13u3"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27855.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "1:2.4.3+dfsg1-1"
          }
        ]
      }
    ],
    "package": {
      "name": "dovecot",
      "purl": "pkg:deb/debian/dovecot?arch=source&distro=forky",
      "ecosystem": "Debian:14"
    },
    "versions": [
      "1:2.4.1+dfsg1-6",
      "1:2.4.1+dfsg1-7",
      "1:2.4.1+dfsg1-8",
      "1:2.4.1+dfsg1-9",
      "1:2.4.2+dfsg1-1",
      "1:2.4.2+dfsg1-2",
      "1:2.4.2+dfsg1-3",
      "1:2.4.2+dfsg1-4"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27855.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  }
]

Publisher severity

No explicit severity was provided.

Event
#56302 · Revision 1
Added to Heist Feed
Publisher date
Read the original announcement

Revision history

  1. DEBIAN-CVE-2026-27855 · Revision 1Source updated