---
id: CVE-2020-4037
aliases:
  - GHSA-5m6c-jp6f-2vcv
  - BIT-oauth2-proxy-2020-4037
title: Open Redirect in OAuth2 Proxy
summary: Open Redirect in OAuth2 Proxy
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N'
vendor: oauth2-proxy
product: github.com/oauth2-proxy/oauth2-proxy
ecosystem: go
affected:
  - 'github.com/oauth2-proxy/oauth2-proxy >= 5.1.1, < 6.0.0'
patched:
  - github.com/oauth2-proxy/oauth2-proxy 6.0.0
published: '2021-12-20'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-5m6c-jp6f-2vcv'
references:
  - url: >-
      https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5m6c-jp6f-2vcv
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2020-4037'
  - url: >-
      https://github.com/oauth2-proxy/oauth2-proxy/commit/ee5662e0f5001d76ec76562bb605abbd07c266a2
  - url: 'https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v6.0.0'
tags:
  - osv
  - go
epss: 0.00896
epssPercentile: 0.58057
ingestedAt: '2026-07-09T18:56:35.935Z'
---

## Overview

### Impact
As users can provide a redirect address for the proxy to send the authenticated user to at the end of the authentication flow. This is expected to be the original URL that the user was trying to access.
This redirect URL is checked within the proxy and validated before redirecting the user to prevent malicious actors providing redirects to potentially harmful sites.

## Affected packages

- `github.com/oauth2-proxy/oauth2-proxy >= 5.1.1, < 6.0.0`

## Remediation

Upgrade to a patched release:

- `github.com/oauth2-proxy/oauth2-proxy 6.0.0`