CVE-2020-11053
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceOAuth2 Proxy before 5.1.1 contains an open redirect vulnerability where the redirect URL validation can be bypassed by crafting a redirect URL with HTML encoded whitespace characters. This allows attackers to redirect authenticated users to arbitrary malicious sites.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 5.1.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Determine OAuth2 Proxy versionRun 'oauth2-proxy --version' or check the binary/package version installed on the systemAffected if The installed version is any version prior to 5.1.1 (versions like 5.1.0, 5.0.0, 4.x, etc.)
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Identify redirect URL configurationInspect the OAuth2 Proxy configuration file (typically oauth2-proxy.cfg, config.yaml, or environment variables) and look for the '--redirect-url' flag or 'redirect_url' settingAffected if A redirect_url is configured that could accept user-supplied input and allows external redirects
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Verify redirect URL validation is in useReview the proxy configuration to confirm the '--proxy-prefix' or similar routing is set up where user-controlled redirects could be passed via the 'rd' query parameterAffected if The proxy allows arbitrary redirect parameters that are not strictly validated against an allowed domain list
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Check for upstream service handlingExamine logs or configuration to see if the proxy is sitting behind a reverse proxy or used in a setup where the 'next' or 'rd' parameter controls navigation after authenticationAffected if The OAuth2 Proxy is configured to redirect users to external URLs based on request parameters without strict allowlist validation
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Test for URL validation bypassIf you have access to a test environment, craft a request with HTML encoded whitespace (e.g., %20 or %09) in the redirect parameter to see if it bypasses domain validationAffected if The validation logic does not normalize or reject URLs with encoded whitespace, allowing redirect to arbitrary domains
You are affected if OAuth2 Proxy version is below 5.1.1 AND the redirect URL parameter is externally controllable without strict domain allowlisting.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor data5.1.1
Upgrade OAuth2 Proxy to version 5.1.1 or later to patch the validation bypass.
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-11053 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-11053 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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