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Oauth2 ProxyApplication · Oauth2 Proxy Project

CVE-2026-40575

CRITICAL · 9.1 CVSS v3.1 Published 2026-04-22
Fix available
A fix is available. Upgrade to 7.15.2 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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 · unedited
OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 may trust a client-supplied `X-Forwarded-Uri` header when `--reverse-proxy` is enabled and `--skip-auth-regex` or `--skip-auth-route` is configured. An attacker can spoof this header so OAuth2 Proxy evaluates authentication and skip-auth rules against a different path than the one actually sent to the upstream application. This can result in an unauthenticated remote attacker bypassing authentication and accessing protected routes without a valid session. Impacted users are deployments that run oauth2-proxy with `--reverse-proxy` enabled and configure at least one `--skip-auth-regex` or `--skip-auth-route` rule. This issue is patched in `v7.15.2`. Some workarounds are available for those who cannot upgrade immediately. Strip any client-provided `X-Forwarded-Uri` header at the reverse proxy or load balancer level; explicitly overwrite `X-Forwarded-Uri` with the actual request URI before forwarding requests to OAuth2 Proxy; restrict direct client access to OAuth2 Proxy so it can only be reached through a trusted reverse proxy; and/or remove or narrow `--skip-auth-regex` / `--skip-auth-route` rules where possible. For nginx-based deployments, ensure `X-Forwarded-Uri` is set by nginx and not passed through from the client.

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 confidence

OAuth2 Proxy versions 7.5.0-7.15.1 trust client-supplied X-Forwarded-Uri headers when --reverse-proxy is enabled with --skip-auth-regex or --skip-auth-route configured. Attackers can spoof this header to make the proxy evaluate authentication and skip-auth rules against a different path than what is actually sent to the upstream, enabling unauthenticated access to protected routes.

MitigationUpgrade to v7.15.2 immediately. If immediate upgrade is not feasible, implement header sanitization at the upstream reverse proxy/load balancer to strip or overwrite X-Forwarded-Uri with the actual request URI before forwarding to OAuth2 Proxy.

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
Oauth2 ProxyApplication
Affected:>= 7.5.0, < 7.15.2

CVSS 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
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check OAuth2 Proxy version
    Run 'oauth2-proxy --version' or check the binary/package version installed (e.g., docker images, package manager)
    Affected if Version is 7.5.0 through 7.15.1 (inclusive)
  2. Verify --reverse-proxy flag is enabled
    Inspect the OAuth2 Proxy startup command or configuration file for the '--reverse-proxy' or 'reverse_proxy: true' setting
    Affected if The --reverse-proxy option is enabled in the configuration
  3. Identify any skip-auth rules
    Review OAuth2 Proxy configuration for 'skip_auth_regex' or 'skip_auth_domains' directives that define paths that bypass authentication
    Affected if Any skip-auth rules are defined, as these can be bypassed via the header spoofing
  4. Assess network exposure
    Determine if OAuth2 Proxy is directly accessible to clients or if it sits behind a reverse proxy that overwrites X-Forwarded-Uri headers before reaching OAuth2 Proxy
    Affected if OAuth2 Proxy is directly accessible to untrusted clients without an upstream proxy that sanitizes X-Forwarded-Uri

Environment is affected if OAuth2 Proxy version is between 7.5.0 and 7.15.1, --reverse-proxy is enabled, skip-auth rules exist, and the proxy is accessible to clients without an upstream that overwrites X-Forwarded-Uri headers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Upgrade available Upgrade to 7.15.2 or later
Fixed in 7.15.2
Interim mitigation

Upgrade to v7.15.2 immediately. If immediate upgrade is not feasible, implement header sanitization at the upstream reverse proxy/load balancer to strip or overwrite X-Forwarded-Uri with the actual request URI before forwarding to OAuth2 Proxy.

Recommended fix High confidence

v7.15.2

  1. Upgrade oauth2-proxy to version 7.15.2 or later

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Oauth2 Proxy Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,770
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,832.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-40575 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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