CVE-2026-42006

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-12 · updated 2026-10-26
Weakness: CWE-400

Description

An attacker can cause uncontrolled memory usage with excessive bracing over IMAP. The fix in CVE-2026-27857 was incomplete, only blocking one way of doing this, so there was still another way left open. In particular, the fix was for closing braces, but you could still use open braces to bypass the limit. Using excessive bracing, attacker can cause memory usage up to configured memory limit. Install fixed version, or configure vsz_limit for imap process to low value. No publicly available exploits are known.

Affected products

dovecot: before 2.4.4 — fixed in 2.4.4
Open-Xchange Dovecot: before 3.1.5 — fixed in 3.1.5

How to fix

Upgrade to a fixed version: dovecot 2.4.4; Open-Xchange Dovecot 3.1.5. Check the vendor advisory for mitigations.

References

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