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

Advisory record · `GHSA-p64j-f4x9-wq66`

- **Identifiers:** `GHSA-p64j-f4x9-wq66` · `CVE-2026-79662` · `GO-2026-5531`
- **State:** Confirmed
- **Severity:** CVSS 8.8 High
- **Critical:** No
- **Weakness (CWE):** [CWE-601](https://cwe.mitre.org/data/definitions/601.html) · [CWE-1173](https://cwe.mitre.org/data/definitions/1173.html)
- **Tags:** [Open redirect](https://agentprime.io/advisories/tag/open-redirect.md) · [CWE-1173](https://agentprime.io/advisories/tag/cwe-1173.md)
- **Published:** 7 May 2026
- **Updated:** 27 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 7 May 2026, 21:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/lin-snow/Ech0` (Go): affected `<1.4.8-0.20260503040728-a7e8b8e84bd1`; fixed in `1.4.8-0.20260503040728-a7e8b8e84bd1`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Ech0 versions before 1.4.8-0.20260503040728-a7e8b8e84bd1 (Go module github.com/lin-snow/Ech0) validate OAuth client redirect URIs by comparing only scheme and host against the admin allowlist, ignoring path, query, and fragment. An attacker who can get a victim to click a crafted OAuth login link, and who can then leak the one-time exchange code from a page on the allowlisted host, can trade that code for the victim's access and refresh tokens and take over the account. Upgrade to 1.4.8-0.20260503040728-a7e8b8e84bd1 or later. The source gives no workaround beyond upgrading.

Written 6 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 8.8 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N`, from CNA (VulnCheck)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0032, the 25th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:48 UTC: First seen by agentprime
- 31 Oct 2026, 14:48 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-p64j-f4x9-wq66)

## Sources

- [GitHub Advisory Database: GHSA-p64j-f4x9-wq66](https://github.com/advisories/GHSA-p64j-f4x9-wq66)
- [OSV: GHSA-p64j-f4x9-wq66](https://osv.dev/vulnerability/GHSA-p64j-f4x9-wq66)
- <https://github.com/lin-snow/Ech0/security/advisories/GHSA-p64j-f4x9-wq66>
- <https://github.com/lin-snow/Ech0/commit/a7e8b8e84bd1e3db090dfb720f2c6c433356b442>
- <https://github.com/lin-snow/Ech0>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-p64j-f4x9-wq66>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-p64j-f4x9-wq66/>. Everything for agents: <https://agentprime.io/llms.txt>.