Headline
CVE-2023-27496: Crash when a redirect url without a state param is received in the oauth filter
Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9, the OAuth filter assumes that a state query param is present on any response that looks like an OAuth redirect response. Sending it a request with the URI path equivalent to the redirect path, without the state parameter, will lead to abnormal termination of Envoy process. Versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9 contain a patch. The issue can also be mitigated by locking down OAuth traffic, disabling the filter, or by filtering traffic before it reaches the OAuth filter (e.g. via a lua script).
Impact
Denial of service (crash).
Affected components
Oauth2
Attack vector/s
If Envoy is running with the OAuth filter enabled exposed, a malicious actor could construct a request which would cause denial of service by crashing Envoy.
Description
The OAuth filter assumes that a state query param is present on any response that looks like an OAuth redirect response. Sending it a request with the URI path equivalent to the redirect path, without the state parameter, will lead to abnormal termination of Envoy process.
Example exploit or proof-of-concept
If the redirect path looks like /oauth_redirect, sending a request to Envoy with the URI path /oauth_redirect and without specifying the state param will lead to a segmentation fault.
Mitigation
The issue can be mitigated by locking down OAuth traffic, disabling the filter or by filtering traffic before it reaches the OAuth filter (e.g. via a lua script).
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