# CVE-2026-73550: Envoy: HTTP/2 Discarded Host Header 200 GB Header-Copy OOM in Envoy

> CVE-2026-73550: Envoy: HTTP/2 Discarded Host Header 200 GB Header-Copy OOM in Envoy. CVSS 7.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-73550
Last updated: 2026-10-05T14:07:45Z

- Published: 2026-09-21 19:49 UTC · Updated: 2026-10-05 14:07 UTC · Assigner: GitHub\_M
- CVSS: 7.5 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS: 0.55%, 46th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-401

## 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.

## Affected vendors and products

- envoyproxy: envoy

## Tracked companies

- [Google Cloud](https://rewindex.com/company/google-cloud.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-73550)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-73550)
- [https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80](https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80)
- [https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2](https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2)
- [https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300](https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300)
- [https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b](https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.36.10](https://github.com/envoyproxy/envoy/releases/tag/v1.36.10)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.37.6](https://github.com/envoyproxy/envoy/releases/tag/v1.37.6)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.38.4](https://github.com/envoyproxy/envoy/releases/tag/v1.38.4)
- [https://github.com/envoyproxy/envoy/releases/tag/v1.39.1](https://github.com/envoyproxy/envoy/releases/tag/v1.39.1)
- [https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh](https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-73550 · Markdown: https://rewindex.com/cve/CVE-2026-73550.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-73550 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:15:23.430Z