{"id":"CVE-2026-73550","published":"2026-09-21T20:17:28.733","lastModified":"2026-09-21T20:17:28.733","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.","cvssScore":7.5,"cvssSeverity":"HIGH","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwes":["CWE-401"],"vendors":[],"products":[],"references":[{"url":"https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80","tags":[]},{"url":"https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2","tags":[]},{"url":"https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300","tags":[]},{"url":"https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.36.10","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.37.6","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.38.4","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.39.1","tags":[]},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh","tags":[]}],"exploitRefs":[{"url":"https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80","tags":[]},{"url":"https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2","tags":[]},{"url":"https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300","tags":[]},{"url":"https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.36.10","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.37.6","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.38.4","tags":[]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.39.1","tags":[]},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh","tags":[]}],"hasPoc":true,"ai":{"summary":"The flaw allows unauthenticated clients to exploit HPACK indexing to submit large Host values, causing out-of-memory issues in Envoy proxies.","exploitability":"Exploitation requires sending multiple HTTP/2 streams with large Host headers; preconditions include the use of affected Envoy versions prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1.","blast_radius":"If exploited, it could lead to Denial of Service (DoS) by overwhelming the proxy with excessive memory usage.","remediation":"Upgrade Envoy to version 1.36.10 or later.","tags":["dos","http2","proxy","memory"],"model":"qwen2.5:7b-instruct","analyzedAt":"2026-09-22T06:13:37.004Z"}}