CVE-2026-73550

high

Envoy is an open source edge and service proxy designed for cloud-native applications.

Vendor / product: Envoyproxy — envoy

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

7.5

7.5 (CVSS v3.1)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Severity source: NVD CVSS v3.1 (security-advisories@github.com)

Timeline (UTC)

Published: 2026-09-21 20:17

Modified: 2026-10-05 14:07

NVD status: Analyzed

Last synced 2 days ago

Verified against the source API 2026-10-27 06:54 UTC

Exploitation

Not listed in CISA KEV (as of last catalog sync)

Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

envoyproxy / envoy <1.36.10, ≥1.37.0 <1.37.6, ≥1.38.0 <1.38.4, ≥1.39.0 <1.39.1

Weakness classification (CWE)

CWE-401

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

Vendor advisory: https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh

Patch / mitigation: https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80

Patch / mitigation: https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2

Patch / mitigation: https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300

Patch / mitigation: https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b

References

https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80 security-advisories@github.com
https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2 security-advisories@github.com
https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300 security-advisories@github.com
https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.36.10 security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.37.6 security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.38.4 security-advisories@github.com
https://github.com/envoyproxy/envoy/releases/tag/v1.39.1 security-advisories@github.com
https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh security-advisories@github.com
https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh 134c704f-9b21-4f2e-91b3-4a467353bcc0

Data sources

NVD CVE API 2.0 — fetched 2026-10-27 06:54 UTC · record ↗

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CVE-2026-73550

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