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OX Dovecot CVE-2026-40013

| EUVDEUVD-2026-67663 MEDIUM
Buffer Underwrite ('Buffer Underflow') (CWE-124)
2026-08-28 OX GHSA-jh33-8ccj-9h78
Denial Of Service RCE Buffer Overflow Ox Dovecot Pro Ox Dovecot Ce
4.3
CVSS 3.1 · Vendor: OX
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Severity by source

Vendor (OX) PRIMARY
4.3 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
vuln.today AI
6.5 MEDIUM

Process crash causes complete ManageSieve unavailability warranting A:H; authentication required (PR:L) and network-reachable; no confidentiality or integrity impact confirmed.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative

Primary rating from Vendor (OX).

CVSS VectorVendor: OX

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

2
Patch available
Aug 28, 2026 - 13:17 EUVD
Analysis Generated
Aug 28, 2026 - 12:11 vuln.today

DescriptionCVE.org

An attacker that has valid credentials can submit a Sieve script containing an extreme numeric literal, which causes an out-of-bounds write when the ManageSieve service compiles the script. This causes memory corruption and an observed crash of the ManageSieve process, resulting in denial of service for script management. This might be able to be used for remote code execution. Disable the ManageSieve service if users do not need remote Sieve script management. Update to non-vulnerable version. No publicly available exploits are known.

AnalysisAI

Memory corruption via out-of-bounds write in OX Dovecot Pro and OX Dovecot CE's ManageSieve service allows authenticated network attackers to crash the ManageSieve process, denying all users the ability to remotely manage Sieve email filter scripts. The root cause is improper handling of extreme numeric literals during Sieve script compilation. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Persist
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Impact
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Vulnerability AssessmentAI

Exploitation The ManageSieve service must be enabled and network-accessible - ManageSieve is not enabled by default in all Dovecot deployments and must be explicitly configured. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The official CVSS 3.1 score of 4.3 (Medium) with vector AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L reflects network-reachable, low-complexity exploitation requiring only low-privilege credentials, but assigns only A:L (low availability impact). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation The vendor recommends two actions: disabling the ManageSieve service if users do not require remote Sieve script management, and updating to the non-vulnerable version. … Detailed patch versions, workarounds, and compensating controls in full report.
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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise High Performance Computing 12 Affected
SUSE Linux Enterprise High Performance Computing 12 Affected
SUSE Linux Enterprise Module for Server Applications 15 SP7 Affected
SUSE Linux Enterprise Module for Server Applications 15 SP7 Affected
SUSE Linux Enterprise Server 15 SP7 Affected

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CVE-2026-40013 vulnerability details – vuln.today
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