CVE-2026-52681
Description
A flaw was found in dovecot. An authenticated attacker can bypass the configured Sieve CPU limit by repeatedly changing active scripts. This action prevents proper CPU resource accounting and leaves behind compiled script files, leading to sustained CPU and increased disk consumption. The consequence is a degradation of service for mail delivery, potentially causing a Denial of Service (DoS).
Mitigation
Administrators can monitor system resources for abnormal CPU usage and disk consumption related to Dovecot Sieve processes. To prevent exploitation, if Sieve functionality is not required, it can be disabled by removing the `sieve` plugin from the `mail_plugins` setting in the Dovecot configuration. Disabling Sieve will impact user mail filtering capabilities. A restart of the Dovecot service is required for configuration changes to take effect.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 3.1 | N/A | 3.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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