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.

CVSS v3 4.3 MEDIUM

4.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact LOW

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

History

30 Apr 2026, 17:42

Type	Values Removed	Values Added
References	~~() https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json -~~	() https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json - Vendor Advisory
First Time		Open-xchange Open-xchange dovecot Dovecot Dovecot dovecot
CPE		cpe:2.3:a:dovecot:dovecot:::::::: cpe:2.3:a:open-xchange:dovecot:::::pro:::*

27 Mar 2026, 09:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-03-27 09:16

Updated : 2026-04-30 17:42

NVD link : CVE-2026-27857

Mitre link : CVE-2026-27857

CVE.ORG link : CVE-2026-27857

JSON object : View

Products Affected

open-xchange

dovecot

dovecot

dovecot

CWE

CWE-400

Uncontrolled Resource Consumption

{"id": "CVE-2026-27857", "cveTags": [], "metrics": {"cvssMetricV31": [{"type": "Secondary", "source": "security@open-xchange.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 4.3, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "LOW", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 1.4, "exploitabilityScore": 2.8}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.5, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 3.9}]}, "published": "2026-03-27T09:16:19.917", "references": [{"url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0001.json", "tags": ["Vendor Advisory"], "source": "security@open-xchange.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "security@open-xchange.com", "description": [{"lang": "en", "value": "CWE-400"}]}], "descriptions": [{"lang": "en", "value": "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."}], "lastModified": "2026-04-30T17:42:47.547", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "BE209329-C5EA-4EE7-A23E-CD2EC061A9A4", "versionEndExcluding": "2.4.3"}, {"criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "vulnerable": true, "matchCriteriaId": "5CF82590-D98A-4E06-AC8C-6CC3506ED923", "versionEndExcluding": "2.3.22.1"}, {"criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "vulnerable": true, "matchCriteriaId": "8476287B-40B2-4533-A3AB-B880516C0B5C", "versionEndExcluding": "3.0.5", "versionStartIncluding": "3.0.0"}, {"criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "vulnerable": true, "matchCriteriaId": "11CA35AA-72CB-4614-A064-8A90F65D8A71", "versionEndExcluding": "3.1.4", "versionStartIncluding": "3.1.0"}], "operator": "OR"}]}], "sourceIdentifier": "security@open-xchange.com"}