Medium [CVE-2026-52687] Denial of Service via IMAP compression memory exhaustion
This medium-severity Red Hat Linux advisory covers CVE-2026-52687 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
An attacker that has valid credentials can select a compression algorithm for the IMAP connection whose decompression state requires a large amount of memory, and open several such connections.
The memory limit of the process is reached with only a few connections, terminating the process and all connections it handles, which can cause degradation or denial of service for IMAP. Alternatively limit the number of connections handled by a single imap-login process, though this has a performance impact.
Update to non-vulnerable version. No publicly available exploits are known.
A flaw was found in dovecot. 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.
Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-770.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9. Will not fix / out of support: Red Hat Enterprise Linux 6.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: dovecot.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Mitigation checklist
- 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.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
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