CVE-2026-79662 Ech0 before 4.7.3 OAuth Redirect URI Validation Bypass

What is CVE-2026-79662?

CVE-2026-79662 is a high-severity vulnerability in lin-snow Ech0, published on 25 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

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.

Weakness: CWE-601

Which versions are affected by CVE-2026-79662?

3 open source packages ship an affected version, including github.com/lin-snow/Ech0 and github.com/lin-snow/ech0.

How do I fix CVE-2026-79662?

Upgrade github.com/lin-snow/Ech0 to 1.4.8-0.20260503040728-a7e8b8e84bd1 or later.

Is CVE-2026-79662 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-79662 exists.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• GitHub advisory
• How this page is made

Also known as GHSA-m5w8-4879-f4pc, GHSA-p64j-f4x9-wq66, GO-2026-5531.