CVE-2025-62504: Envoyproxy Envoy

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

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 products

• Envoyproxy Envoy: before 1.33.12 (fixed in 1.33.12); from 1.34.0, before 1.34.10 (fixed in 1.34.10); from 1.35.0, before 1.35.6 (fixed in 1.35.6); from 1.36.0, before 1.36.2 (fixed in 1.36.2)

Published 2025-10-16. Last modified 2026-10-09.