# CVE-2026-79662: Ech0 OAuth redirect URI validation bypass

Source: https://junglewise.ai/threats/cve-2026-79662-ech0-oauth-redirect-uri-validation-bypass  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-25. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-79662 · Severity: high · CVSS 8 · Published 2026-08-25

Ech0 is an open-source authentication and identity management service. A vulnerability in its OAuth login flow allows attackers to redirect users to arbitrary paths on allowed hosts and capture their authentication credentials. An attacker can trick users into logging in via a crafted link, intercept the temporary authorization code, and trade it for the victim's access and refresh tokens—effectively hijacking their account.

Technologies: [github.com/lin-snow/ech0 (Go)](https://junglewise.ai/threats/technologies/github-com-lin-snow-ech0), [Lin-Snow Ech0](https://junglewise.ai/threats/technologies/ech0). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Lin-Snow](https://junglewise.ai/threats/vendors/lin-snow).

## Quick answers

**Is CVE-2026-79662 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-79662 being exploited in the wild.

**How severe is CVE-2026-79662?** High severity, with a CVSS score of 8, published 25 August 2026.

**Which products and versions are affected?** github.com/lin-snow/ech0 (Go) SEMVER:introduced=0,fixed=1.4.8-0.20260503040728-a7e8b8e84bd1; Lin-Snow Ech0 through 4.5.6.

**Is there a fix for CVE-2026-79662?** Yes. github.com/lin-snow/ech0 (Go): upgrade to 1.4.8-0.20260503040728-a7e8b8e84bd1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-79662 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-79662?** Check whether you run github.com/lin-snow/ech0 (Go) or Lin-Snow Ech0 at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/lin-snow/ech0 (Go): upgrade to 1.4.8-0.20260503040728-a7e8b8e84bd1 or later

  ```sh
  go get github.com/lin-snow/ech0@v1.4.8-0.20260503040728-a7e8b8e84bd1
  ```


## Technical details

The vulnerability lies in parseAndValidateClientRedirect (internal/service/auth/auth.go:448), which validates OAuth redirect URIs by comparing only the scheme and host components against an admin-configured allowlist, ignoring path, query, and fragment. The caller-supplied redirect_uri is embedded into a signed state JWT at login time without validation. An attacker crafts a redirect_uri with a host matching an allowed origin but a path under attacker control; after OAuth provider exchange, Ech0 redirects the victim to that path with the one-time exchange code in the query string. If the code is leaked via Referer header, analytics, or an open redirect on the matched host, the attacker can exchange it at the public POST /api/auth/exchange endpoint for the victim's tokens. The vulnerability violates RFC 6749 §3.1.2 (exact redirect URI matching). Fixed in version 4.7.3.

## Affected products

- lin-snow Ech0 through 4.5.6

## Identifiers

- CVE-2026-79662
- GHSA-p64j-f4x9-wq66
- GO-2026-5531

## Timeline

- 2026-05-03: disclosed
- 2026-04-01: patched: Fix released in version 4.7.3
- 2026-08-25: advisory

## References

- [https://github.com/lin-snow/Ech0/security/advisories/GHSA-p64j-f4x9-wq66](https://github.com/lin-snow/Ech0/security/advisories/GHSA-p64j-f4x9-wq66)
- [https://www.vulncheck.com/advisories/ech0-before-oauth-redirect-uri-validation-bypass](https://www.vulncheck.com/advisories/ech0-before-oauth-redirect-uri-validation-bypass)

## Related threats

- [Ech0 scope bypass in PUT /user endpoint via profile:read token](https://junglewise.ai/threats/cve-2026-79673-ech0-scope-bypass-in-put-user-endpoint-via-profile-read-token)
- [Ech0 authorization bypass in comment panel endpoints](https://junglewise.ai/threats/cve-2026-79672-ech0-authorization-bypass-in-comment-panel-endpoints)
- [Ech0 server-side request forgery in webhook URL validation](https://junglewise.ai/threats/cve-2026-79671-ech0-server-side-request-forgery-in-webhook-url-validation)
- [Ech0 stored cross-site scripting in file upload](https://junglewise.ai/threats/cve-2026-79670-ech0-stored-cross-site-scripting-in-file-upload)
- [Ech0 missing authorization on system log endpoints](https://junglewise.ai/threats/cve-2026-79669-ech0-missing-authorization-on-system-log-endpoints)