CVE-2026-40016

Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130 times of the configured limit. Attacker can use this to degrade server performance and bypass configured CPU time limits for Sieve scripts. Install fixed version, or alternatively prevent direct access to Sieve scripts via ManageSieve or local access. No publicly available exploits are known.

CVSS v3 5.3 MEDIUM

5.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 1.6 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0002.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, 18:10

Type	Values Removed	Values Added
Summary		(es) El atacante puede cargar un script Sieve malicioso a través del servicio ManageSieve (o localmente) para eludir los límites de tiempo de CPU configurados para Sieve hasta 130 veces el límite configurado. El atacante puede usar esto para degradar el rendimiento del servidor y eludir los límites de tiempo de CPU configurados para los scripts Sieve. Instale la versión corregida o, alternativamente, impida el acceso directo a los scripts Sieve a través de ManageSieve o acceso local. No se conocen exploits disponibles públicamente.

Information

Published : 2026-05-12 14:17

Updated : 2026-10-26 18:10

NVD link : CVE-2026-40016

Mitre link : CVE-2026-40016

CVE.ORG link : CVE-2026-40016

JSON object : View

Products Affected

open-xchange

dovecot

dovecot

dovecot

CWE

CWE-400

Uncontrolled Resource Consumption

{"id": "CVE-2026-40016", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-40016", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-05-12T15:38:37.399932Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "security@open-xchange.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.3, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 1.6}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 6.5, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "LOW", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 2.8}]}, "affected": [{"source": "security@open-xchange.com", "affectedData": [{"vendor": "Open-Xchange GmbH", "modules": ["core"], "product": "OX Dovecot Pro", "versions": [{"status": "affected", "version": "0", "versionType": "semver", "lessThanOrEqual": "2.3.0"}], "defaultStatus": "unaffected"}]}], "published": "2026-05-12T14:17:03.570", "references": [{"url": "https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0002.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": "Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130 times of the configured limit. Attacker can use this to degrade server performance and bypass configured CPU time limits for Sieve scripts. Install fixed version, or alternatively prevent direct access to Sieve scripts via ManageSieve or local access. No publicly available exploits are known."}, {"lang": "es", "value": "El atacante puede cargar un script Sieve malicioso a trav\u00e9s del servicio ManageSieve (o localmente) para eludir los l\u00edmites de tiempo de CPU configurados para Sieve hasta 130 veces el l\u00edmite configurado. El atacante puede usar esto para degradar el rendimiento del servidor y eludir los l\u00edmites de tiempo de CPU configurados para los scripts Sieve. Instale la versi\u00f3n corregida o, alternativamente, impida el acceso directo a los scripts Sieve a trav\u00e9s de ManageSieve o acceso local. No se conocen exploits disponibles p\u00fablicamente."}], "lastModified": "2026-10-26T18:10:00.173", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "86CE1F3B-DF73-431A-9EC0-491E8969A187", "versionEndExcluding": "2.4.4"}, {"criteria": "cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*", "vulnerable": true, "matchCriteriaId": "28C2DD58-A4B0-4F2C-BC60-F30F380251BC", "versionEndExcluding": "3.1.5"}], "operator": "OR"}]}], "sourceIdentifier": "security@open-xchange.com"}