CVE-2026-73549: Envoyproxy Envoy

Medium severity, CVSS 5.3. EPSS: 0.6% chance of exploitation in the next 30 days.

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1, Envoy's Utility::copyInternetAddressAndPort and QUIC client-address paths reconstruct scoped IPv6 addresses through addressAsString and Ipv6Instance. The string includes a percent scope identifier that inet_pton cannot parse, causing an exception or abort. Kernel-provided scoped IPv6 destinations in ORIGINAL_DST transparent-proxy deployments, and affected QUIC connection paths, can therefore terminate the process. The relevant scope boundary is that the HTTP use_http_header override rejects scoped addresses earlier; the advisory's crash path requires a kernel-provided original destination or the affected QUIC path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

Affected products

• Envoyproxy Envoy: before 1.36.10 (fixed in 1.36.10); from 1.37.0, before 1.37.6 (fixed in 1.37.6); from 1.38.0, before 1.38.4 (fixed in 1.38.4); from 1.39.0, before 1.39.1 (fixed in 1.39.1)

Published 2026-09-21. Last modified 2026-10-05.