Vulnerability · Published Aug 25, 2026 · Assigned by VulnCheck
CVE-2026-79662Ech0 before 4.7.3 OAuth Redirect URI Validation Bypass
High 8.0
In plain English
A high-severity open redirect in Ech0 from lin-snow. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 25% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Ech0 through 4.5.6 contains an OAuth redirect URI validation vulnerability in parseAndValidateClientRedirect (internal/service/auth/auth.go) that compares only the scheme and host of the client-supplied redirect_uri against the admin-configured allowlist, ignoring path, query, and fragment components. The redirect_uri is embedded into the signed state JWT at login time without validation. An attacker can craft a redirect_uri whose host matches an allowed origin but whose path is attacker-influenced; after the OAuth exchange the victim is redirected to that path with a one-time exchange code in the query string. If the code leaks (e.g., via Referer, analytics, or an open redirect on that host), the attacker can trade it at the public POST /api/auth/exchange endpoint for the victim's access and refresh tokens. Fixed in 4.7.3.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/lin-snow/Ech0 | 1.4.8-0.20260503040728-a7e8b8e84bd1 | GHSA-p64j-f4x9-wq66 |
| Go | github.com/lin-snow/ech0 | 1.4.8-0.20260503040728-a7e8b8e84bd1 | GO-2026-5531 |
Affected products (as reported)
Weakness: CWE-601 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N
References
- GitHub Security Advisory (GHSA-p64j-f4x9-wq66) vendor-advisory
- VulnCheck Advisory: Ech0 before 4.7.3 OAuth Redirect URI Validation Bypass third-party-advisory