CVE-2020-11053
MEDIUMCVE-2020-11053 is a medium-severity (CVSS 6.1) Open Redirect vulnerability in github.com/oauth2-proxy/oauth2-proxy. O3 Security confirms whether CVE-2020-11053 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Open Redirect in OAuth2 Proxy
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2020-11053.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2020-11053 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 365,017 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/oauth2-proxy/oauth2-proxyReal-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 before 5.1.1, there is an open redirect vulnerability. 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. However, by crafting a redirect URL with HTML encoded whitespace characters the validation could be bypassed and allow a redirect to any URL provided. This has been patched in 5.1.1.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/oauth2-proxy/oauth2-proxy | all versions | 5.1.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/oauth2-proxy/oauth2-proxy. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/oauth2-proxy/oauth2-proxy to 5.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-11053 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2020-11053 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2020-11053. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2020-11053 in your dependencies?
O3 detects CVE-2020-11053 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.