CVE-2026-26312 Stalwart Mail Server has Out-of-Memory Denial of Service via Malformed Nested MIME Messages
Attackers can crash Stalwart Mail Server by sending malformed nested MIME emails, causing excessive resource consumption and out-of-memory conditions.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-26312?
CVE-2026-26312 is a medium-severity denial of service vulnerability in stalwartlabs stalwart, published on 19 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-770
Which versions are affected by CVE-2026-26312?
It affects 1 product.
Products include Stalw Stalwart.
How do I fix CVE-2026-26312?
No fix has been published for CVE-2026-26312 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-26312 being exploited?
There is no known exploitation of CVE-2026-26312 in the wild and no public exploit code.
Sources
Also known as GHSA-jm95-876q-c9gw.