CVE-2026-73550: Envoy: HTTP/2 Discarded Host Header 200 GB Header-Copy OOM in Envoy
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.
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H · CWE-401
Tracked companies
Mapped from the CVE’s affected-product data, NVD CPE matches, vendor advisories or package feeds. A mapping means the vendor’s software is named, not that its hosted service was exposed.
Status incidents that name it
No tracked status incident names this CVE.
Affected vendors and products
envoyproxy: envoy
References
- CVE record on cve.org (opens in new tab)
- NVD entry (opens in new tab)
- github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80 (opens in new tab)
- github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2 (opens in new tab)
- github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300 (opens in new tab)
- github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b (opens in new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.36.10 (opens in new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.37.6 (opens in new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.38.4 (opens in new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.39.1 (opens in new tab)
- github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh (opens in new tab)
- CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (opens in new tab)
- This product uses data from the NVD API but is not endorsed or certified by the NVD. (opens in new tab)
- Known Exploited Vulnerabilities catalog from CISA. (opens in new tab)
- EPSS scores from FIRST (Exploit Prediction Scoring System). (opens in new tab)