Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Envoyproxy | Envoy | < 1.36.10 |
Related Weaknesses (CWE)
References
- https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01Patch
- https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd3Patch
- https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512Patch
- https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84fPatch
- https://github.com/envoyproxy/envoy/releases/tag/v1.36.10Release Notes
- https://github.com/envoyproxy/envoy/releases/tag/v1.37.6Release Notes
- https://github.com/envoyproxy/envoy/releases/tag/v1.38.4Release Notes
- https://github.com/envoyproxy/envoy/releases/tag/v1.39.1Release Notes
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvhExploitVendor Advisory
- https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvhExploitVendor Advisory
FAQ
What is CVE-2026-73550?
CVE-2026-73550 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 discardi...
How severe is CVE-2026-73550?
CVE-2026-73550 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-73550?
Check the references section above for vendor advisories and patch information. Affected products include: Envoyproxy Envoy.