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.

Database specific

{
    "cwe_ids": [
        "CWE-294"
    ],
    "cna_assigner": "OX",
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27855.json",
    "unresolved_ranges": [
        {
            "extracted_events": [
                {
                    "last_affected": "2.3.0"
                }
            ],
            "source": "AFFECTED_FIELD"
        }
    ]
}

References

Affected packages

Git / github.com/dovecot/core

Affected ranges

Type

GIT

Repo

https://github.com/dovecot/core

Events

Introduced

Fixed

c1b22ef978ca72999e254b2f3964b3d32d1a4979

Database specific

{
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "fixed": "2.4.3"
        }
    ],
    "source": "CPE_RANGE",
    "cpe": "cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*"
}

Affected versions

1.*

1.1.alpha1

1.1.alpha2

1.1.alpha4

1.1.alpha5

1.1.alpha6

1.1.beta1

1.1.beta10

1.1.beta11

1.1.beta12

1.1.beta13

1.1.beta14

1.1.beta16

1.1.beta2

1.1.beta3

1.1.beta4

1.1.beta5

1.1.beta6

1.1.beta8

1.1.beta9

1.1.rc1

1.1.rc2

1.1.rc3

1.2.alpha1

1.2.alpha2

1.2.alpha3

1.2.alpha4

1.2.alpha5

1.2.beta1

1.2.beta2

1.2.beta3

1.2.beta4

1.2.rc1

2.*

2.0.0

2.0.1

2.0.2

2.0.3

2.0.4

2.0.5

2.0.6

2.0.7

2.0.8

2.0.alpha1

2.0.alpha2

2.0.alpha3

2.0.beta1

2.0.beta2

2.0.beta3

2.0.beta4

2.0.beta5

2.0.beta6

2.0.rc1

2.0.rc2

2.0.rc3

2.0.rc4

2.0.rc5

2.0.rc6

2.1.alpha1

2.1.alpha2

2.1.beta1

2.1.rc1

2.1.rc2

2.1.rc3

2.1.rc4

2.1.rc5

2.1.rc6

2.2.0

2.2.1

2.2.10

2.2.11

2.2.12

2.2.13

2.2.13.rc1

2.2.14

2.2.14.rc1

2.2.15

2.2.16

2.2.16.rc1

2.2.17

2.2.17.rc1

2.2.17.rc2

2.2.18

2.2.19

2.2.19.rc1

2.2.19.rc2

2.2.2

2.2.20

2.2.20.rc1

2.2.3

2.2.4

2.2.5

2.2.6

2.2.7

2.2.8

2.2.9

2.2.alpha1

2.2.beta1

2.2.beta2

2.2.rc1

2.2.rc2

2.2.rc3

2.2.rc4

2.2.rc5

2.2.rc6

2.2.rc7

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-27855.json"