CVE-2023-27496: Envoy may crash when a redirect url without a state param is received in the oauth filter

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2023-04-04 · updated 2026-06-17
Weakness: CWE-20

Description

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).

Affected products

envoyproxy envoy: before 1.22.9; from 1.23.0 before 1.23.6; from 1.24.0 before 1.24.4; from 1.25.0 before 1.25.3 — fixed in 1.22.9, 1.23.6, 1.24.4, 1.25.3

How to fix

Upgrade to a fixed version: envoyproxy envoy 1.22.9, 1.23.6, 1.24.4, 1.25.3. Check the vendor advisory for mitigations.

References

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