What’s Vulnerable › Vulnerabilities
CVE-2026-26312: Stalwart Mail Server has Out-of-Memory Denial of Service via Malformed Nested MIME Messages
- Severity: medium (CVSS 6.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.4% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2026-02-19 · updated 2026-06-17
- Weakness: CWE-770
Description
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
- stalwartlabs stalwart: from 0.13.0 before 0.15.5 — fixed in 0.15.5
How to fix
Upgrade to a fixed version: stalwartlabs stalwart 0.15.5. Check the vendor advisory for mitigations.
References
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