Ech0's OAuth redirect URI validation ignores path component, enables exchange-code theft

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary parseAndValidateClientRedirect at internal/service/auth/auth.go:448 validates OAuth client-redirect URIs by comparing only scheme and host against the admin-configured allowlist. Path, query, and fragment are ignored. The initiator at /oauth/:provider/login embeds the caller-supplied redirecturi verbatim into the signed state JWT without any validation at login time. Alice submits a crafted redirecturi whose host matches an allowed origin but whose path points to any page on that host. After the provider exchange, Ech0 redirects the victim to the attacker-chosen path with the one-time exchange code in the query string. If the chosen path leaks the URL via Referer, analytics, or an open redirect, the attacker trades the code at POST /api/auth/exchange for the victim's access and refresh tokens. RFC 6749 §3.1.2 requires exact redirect URI matching. Details Validation at internal/service/auth/auth.go:448: Scheme and host compared via EqualFold. Path, query, fragment all ignored.…

Published by the source

7 May 2026, 21:30 UTC

Last modified by the source

7 May 2026, 21:30 UTC

Source last checked

26 Oct 2026, 15:20 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-p64j-f4x9-wq66

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# Patch Next advisory brief: GHSA-p64j-f4x9-wq66

Advisory: Ech0's OAuth redirect URI validation ignores path component, enables exchange-code theft
IDs: GHSA-p64j-f4x9-wq66
Record: https://patchnext.com/advisories/ghsa-p64j-f4x9-wq66 (revision 1, source checked 26 Oct 2026, 15:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/lin-snow/Ech0 1.4.8-0.20260503040728-a7e8b8e84bd1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/lin-snow/Ech0: affected < 1.4.8-0.20260503040728-a7e8b8e84bd1; fixed in 1.4.8-0.20260503040728-a7e8b8e84bd1

## Suggested inspection (read-only)
- Go github.com/lin-snow/Ech0: 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/lin-snow/Ech0.
- 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://github.com/advisories/GHSA-p64j-f4x9-wq66 (GitHub-reviewed advisory GHSA-p64j-f4x9-wq66 lists affected ranges: Go github.com/lin-snow/Ech0 >=0 <1.4.8-0.20260503040728-a7e8b8e84bd1)

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