CVE-2026-73550: envoyproxy envoy

Vulnerability summary

CVE-2026-73550 is a high (CVSS 7.5) vulnerability in envoyproxy envoy. EPSS estimates a 0.55% chance of exploitation in the next 30 days, higher than 45.3% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 21-09-2026
   PublishedVulnerability first disclosed.
2. 28-09-2026
   Last modifiedVulnerability information updated.

Description

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 copies every decoded HTTP/2 Host header value before discarding it when :authority is already present. The discarded value bypasses saveHeader, so its bytes and count are not charged against request header limits. An unauthenticated client can use HPACK indexing to submit many references to a large Host value across a bounded number of streams, forcing extreme header-copy allocation and causing the proxy to be out-of-memory killed. The relevant scope boundary is that the demonstrated amplification uses HTTP/2 HPACK and the duplicate Host discard behavior. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1.

• CWE-401Missing Release of Memory after Effective LifetimeThe product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.