CVE-2026-67448 Mailpit: WebSocket origin check bypass via percent-encoded path (regression of CVE-2026-22689)
Attackers can bypass WebSocket origin checks via percent-encoded paths to read live email metadata from unauthenticated Mailpit instances.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-67448?
CVE-2026-67448 is a medium-severity vulnerability in axllent mailpit, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Mailpit is an email testing tool and API for developers. From 1.29.0 until 1.30.6, Mailpit's server/server.go origin middleware checks the raw RequestURI for the /api/ prefix while Go's ServeMux routes using the percent-decoded URL path, and server/websockets/client.go configures websocket.Upgrader.CheckOrigin to return true. A malicious website can request /%61pi/events, skip corsOriginAccessControl(), reach the /api/events WebSocket handler, and receive live message IDs, Message-Id values, sender and recipient fields, subjects, tags, and body snippets from an unauthenticated default Mailpit instance after the user visits the site. This is a regression of the earlier WebSocket origin protection and does not affect deployments protected by --ui-auth-file. This issue is fixed in version 1.30.6.
Which versions are affected by CVE-2026-67448?
3 open source packages ship an affected version, including github.com/axllent/mailpit.
| Package | Affected | Fixed in |
|---|---|---|
github.com/axllent/mailpit Go | From 1.29.0 | 1.30.6 |
github.com/axllent/mailpit Go | From 1.29.0 | 1.30.6 |
github.com/axllent/mailpit Go | From 1.29.0 | 1.30.6 |
How do I fix CVE-2026-67448?
Upgrade github.com/axllent/mailpit to 1.30.6 or later.
Is CVE-2026-67448 being exploited?
There is no known exploitation of CVE-2026-67448 in the wild and no public exploit code.
Sources
Also known as GHSA-8r62-w5wh-fc5m, GO-2026-6271.