CVE-2026-27857

Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known.

Database specific

{
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "last_affected": "2.3.0"
                }
            ]
        }
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27857.json",
    "cwe_ids": [
        "CWE-400"
    ],
    "cna_assigner": "OX"
}

References

Affected packages

Git / github.com/dovecot/core

Affected ranges

Type

GIT

Repo

https://github.com/dovecot/core

Events

Introduced

Fixed

c1b22ef978ca72999e254b2f3964b3d32d1a4979

Database specific

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

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/cve-osv-conversion/osv-output/CVE-2026-27857.json"