CVE-2026-47221 remediation guide

envoyproxy envoy

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...

Open CVE record

Productenvoyproxy envoy

Affected versions>= 1.38.0, < 1.38.3, >= 1.37.0, < 1.37.5, >= 1.36.0, < 1.36.9, >= 1.18.0, < 1.35.13, >= 1.18.0 < 1.35.13, >= 1.36.0 < 1.36.9, >= 1.37.0 < 1.37.5, >= 1.38.0 < 1.38.3

Fixed versions1.35.13, 1.36.9, 1.37.5, 1.38.3

Priority basisReview · CVSS 7.5 · EPSS 0.33%

Identify the affected asset

Confirm whether envoyproxy envoy is installed, record the deployed version and installation path, and identify exposed interfaces.

Record the product name, package or appliance identifier, and installed version.
Identify internet-facing, administrative, API, and internal access paths.
Preserve the pre-change configuration and relevant service logs.

Validate the affected-version match

Compare the deployed version with the affected range: >= 1.38.0, < 1.38.3, >= 1.37.0, < 1.37.5, >= 1.36.0, < 1.36.9, >= 1.18.0, < 1.35.13, >= 1.18.0 < 1.35.13, >= 1.36.0 < 1.36.9, >= 1.37.0 < 1.37.5, >= 1.38.0 < 1.38.3. Treat incomplete inventory results as unresolved.

Prioritize with independent signals

The CVSS severity warrants an early asset and exposure review. Combine this signal with asset criticality, exposure, compensating controls, and business impact.

Apply supported remediation

Follow the vendor advisory or supported update path. Current fixed-version status: 1.35.13, 1.36.9, 1.37.5, 1.38.3. Preserve configuration and rollback material before change.

Verify the result

Confirm the resulting version, service health, authentication and access paths, monitoring coverage, and relevant security logs.

Confirm the expected version and package state.
Run a functional health check for critical service paths.
Review authentication, error, application, and security monitoring logs.
Reassess exposure if the supported fix cannot be applied.

Operational boundary

This page does not replace the vendor advisory, support contract, change-management process, or recovery plan. Do not infer that an asset is unaffected from an incomplete inventory query or a missing fixed-version field.