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MEDIUM severity

Open Redirect in OAuth2 ProxyGHSA-5m6c-jp6f-2vcv

MEDIUMFix: oauth2-proxy/oauth2-proxy@ee5662e

GHSA-5m6c-jp6f-2vcv is a medium-severity (CVSS 4.3) Open Redirect vulnerability in github.com/oauth2-proxy/oauth2-proxy. A fix is available for github.com/oauth2-proxy/oauth2-proxy — see the affected versions and patch details below.

Also known asBIT-oauth2-proxy-2020-4037CVE-2020-4037
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs58th percentile — riskier than 58% of all scored CVEsHighest risk
0.00%0.47%0.93%1.40%0.4%0.4%0.9%0.9%0.9%May 26Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-5m6c-jp6f-2vcv by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐹github.com/oauth2-proxy/oauth2-proxy

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

In OAuth2 Proxy from version 5.1.1 and less than version 6.0.0, 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. This has been fixed in version 6.0.0.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/oauth2-proxy/oauth2-proxy≥ 5.1.1&&< 6.0.06.0.0go get github.com/oauth2-proxy/oauth2-proxy@v6.0.0

Affected Products

1 product · 1 configurations
Application
oauth2 proxyoauth2_proxy_project
≥ 5.1.1 && < 6.0.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/oauth2-proxy/oauth2-proxy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update github.com/oauth2-proxy/oauth2-proxy to 6.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5m6c-jp6f-2vcv is resolved across your whole dependency graph.

  3. Workarounds

    Stop reflecting attacker-controlled destinations: resolve every redirect target against an allowlist of paths or hosts you own, prefer a server-side key over a full URL in the request, and reject absolute URLs entirely where the flow only ever needs a relative one.

Frequently Asked Questions

### 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.
O3 Security · Impact-Aware SCA

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Open Redirect in OAuth2 Proxy (Medium 4.3)