CVE-2026-52687
Description
A flaw was found in dovecot. A remote attacker with valid credentials can exploit this vulnerability by selecting a compression algorithm for the IMAP connection that requires a large amount of memory for decompression. By opening several such connections, the attacker can exhaust the process's memory limit, leading to the termination of the process and all its connections. This can cause degradation or a complete denial of service for IMAP.
Mitigation
To mitigate this vulnerability, disable IMAP compression in the Dovecot configuration. This can be achieved by ensuring that `zlib` or other compression plugins are not loaded for IMAP services. For example, remove `zlib` from the `mail_plugins` setting in `dovecot.conf` or a relevant configuration file. A restart of the Dovecot service is required for the changes to take effect. Disabling compression may result in increased network bandwidth usage for IMAP connections.
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 | 6.5 | N/A | 6.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| 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 | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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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