Envoy is an open source edge and service proxy

Overview

Envoy is an open source edge and service proxy. Envoy versions earlier than 1.36.2, 1.35.6, 1.34.10, and 1.33.12 contain a use-after-free vulnerability in the Lua filter. When a Lua script executing in the response phase rewrites a response body so that its size exceeds the configured per_connection_buffer_limit_bytes (default 1MB), Envoy generates a local reply whose headers override the original response headers, leaving dangling references and causing a crash. This results in denial of service. Updating to versions 1.36.2, 1.35.6, 1.34.10, or 1.33.12 fixes the issue. Increasing per_connection_buffer_limit_bytes (and for HTTP/2 the initial_stream_window_size) or increasing per_request_buffer_limit_bytes / request_body_buffer_limit can reduce the likelihood of triggering the condition but does not correct the underlying memory safety flaw.

Affected

• envoy < 1.33.12
• envoy >= 1.34.0, < 1.34.10
• envoy >= 1.35.0, < 1.35.6
• envoy >= 1.36.0, < 1.36.2

Remediation

Upgrade past the affected range:

• envoy 1.36.2