Mailpit: WebSocket origin check bypass via percent-encoded path (regression of CVE-2026-22689)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-67448: 0.22% estimated exploitation activity in the next 30 days; percentile 12.70 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The cross-site WebSocket hijacking fix was reimplemented as an origin check gated on a raw-URI prefix test, but Go's ServeMux routes on the percent-decoded path, so requesting /%61pi/events reaches the WebSocket handler while skipping the only origin control, and the upgrader itself accepts every origin. Confirmed at HEAD 408b30d. Affects 1.29.0 through 1.30.5. The defect Two halves that were each correct in isolation. server/websockets/client.go accepts any origin and delegates the check elsewhere: server/server.go performs that check but keys it on the RAW request target: r.RequestURI is the untouched wire target; Go's ServeMux routes on the percent-DECODED path. So for /%61pi/events: strings.HasPrefix("/%61pi/events", "/api/") is FALSE (origin check skipped), ServeMux decodes %61 to "a" and routes to /api/events, and the upgrader's CheckOrigin returns true. Measured, default config, no auth: /api/events with Origin: https://evil.example returns 403; /%61pi/events with the…

Published by the source

20 Aug 2026, 21:34 UTC

Last modified by the source

2 Sep 2026, 23:41 UTC

Source last checked

26 Oct 2026, 15:28 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8r62-w5wh-fc5m

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6271

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-8r62-w5wh-fc5m

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# Patch Next advisory brief: CVE-2026-67448

Advisory: Mailpit: WebSocket origin check bypass via percent-encoded path (regression of CVE-2026-22689)
IDs: CVE-2026-67448, GHSA-8r62-w5wh-fc5m
Record: https://patchnext.com/advisories/cve-2026-67448 (revision 3, source checked 26 Oct 2026, 15:28 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/axllent/mailpit 1.30.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/axllent/mailpit: affected >= 1.29.0, <= 1.30.5; fixed in 1.30.6

## Suggested inspection (read-only)
- Go github.com/axllent/mailpit: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/axllent/mailpit.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-8r62-w5wh-fc5m (OSV record GHSA-8r62-w5wh-fc5m lists affected ranges: Go github.com/axllent/mailpit >=1.29.0 <1.30.6 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6271 (OSV record GO-2026-6271 lists affected ranges: Go github.com/axllent/mailpit >=1.29.0 <1.30.6 (fixed))
- Verified: https://github.com/advisories/GHSA-8r62-w5wh-fc5m (GitHub-reviewed advisory GHSA-8r62-w5wh-fc5m lists affected ranges: Go github.com/axllent/mailpit >=1.29.0 <=1.30.5)

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