CVE-2026-47221
MediumCVSS 5.9Exploitation Probability (EPSS)
Low risk36th percentile — higher than 36% of all known CVEs
Summary
Envoy contains a null pointer dereference vulnerability in the router filter when handling HTTP 303 internal redirects for body-less requests (POST, PUT, DELETE, PATCH). An attacker can send such a request to a properly configured route, causing a crash of the entire Envoy process.
Risk Assessment
An unauthenticated attacker can exploit this vulnerability to cause a complete denial of service (DoS), terminating all active connections and making the application unavailable.
Recommendation
It is recommended to immediately upgrade Envoy to version 1.35.13, 1.36.9, 1.37.5, or 1.38.3. If an upgrade is not possible, temporarily disable the 303 response code in the internal redirect policy.
Original NVD description (English source)
Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.18.0 until 1.35.13, 1.36.9, 1.37.5, and 1.38.3, the router filter contains a null pointer dereference vulnerability when handling HTTP 303 (See Other) internal redirects for body-less non-GET/HEAD requests. When a POST, PUT, DELETE, or PATCH request without a body is sent to a route configured with internal redirect policy that includes 303 in redirect_response_codes, and the upstream responds with HTTP 303, the redirect handling code attempts to drain a request body buffer that was never allocated. This results in a segmentation fault that crashes the entire Envoy process. When route configured with internal_redirect_policy including 303 in redirect_response_codes and upstream must return HTTP 303 response, an unauthenticated attacker can exploit this to cause complete denial of service, terminating all active connections. This vulnerability is fixed in 1.35.13, 1.36.9, 1.37.5, and 1.38.3.