CVE-2026-26312: Stalw Stalwart

Medium severity, CVSS 6.5. EPSS: 0.5% chance of exploitation in the next 30 days.

Stalwart is a mail and collaboration server. A denial-of-service vulnerability exists in Stalwart Mail Server versions 0.13.0 through 0.15.4 where accessing a specially crafted email containing malformed nested `message/rfc822` MIME parts via IMAP or JMAP causes excessive CPU and memory consumption, potentially leading to an out-of-memory condition and server crash. The malformed structure causes the `mail-parser` crate to produce cyclical references in its parsed representation, which Stalwart then follows indefinitely. Version 0.15.5 contains a patch.

Affected products

• Stalw Stalwart: from 0.13.0, before 0.15.5 (fixed in 0.15.5)

Published 2026-02-19. Last modified 2026-06-17.