CVE-2026-47221: Envoy: Null pointer deref in internal redirects

Vulnerability summary

CVE-2026-47221 is a high (CVSS 7.5) NULL Pointer Dereference vulnerability in envoyproxy envoy. EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 37.6% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 26-06-2026
   PublishedVulnerability first disclosed.
2. 26-06-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-476NULL Pointer DereferenceThe product dereferences a pointer that it expects to be valid but is NULL.