Answer in brief
CVE-2026-73550 records a Unknown severity vulnerability in Envoy: HTTP/2 Discarded Host Header 200 GB Header-Copy OOM in Envoy. The current sources do not mark it as known exploited. The current feed maps envoyproxy/envoy (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps envoyproxy/envoy (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| envoyproxy/envoygeneric | < 1.36.10 || >= 1.37.0, < 1.37.6 || >= 1.38.0, < 1.38.4 || >= 1.39.0, < 1.39.1 | Not reported |
Published upstream
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 21, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 21, 2026
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.
Quoted source text, attributed separately from HOL analysis.