--- title: "CVE-2026-73548: Envoy - HTTP Request Smuggling" description: "Envoy < 1.36.10, 1.37.6, 1.38.4, and 1.39.1 contains an HTTP request smuggling caused by improper handling of non-WebSocket HTTP upgrades, letting unauthenticated HTTP/2 clients smuggle requests and receive responses intended for others, exploit requires specific upgrade configurations." url: https://panop.io/threat-heartbeat/CVE-2026-73548/ --- # CVE-2026-73548 Envoy - HTTP Request Smuggling Envoy < 1.36.10, 1.37.6, 1.38.4, and 1.39.1 contains an HTTP request smuggling caused by improper handling of non-WebSocket HTTP upgrades, letting unauthenticated HTTP/2 clients smuggle requests and receive responses intended for others, exploit requires specific upgrade configurations. CVSS base score 7.5 /10 High CISA KEV Not listed Public exploit Proof of concept available EPSS 0.46% chance of exploitation in 30 days [View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-73548) ## Details Type HTTP Request Smuggling Impact Information Disclosure CVSS vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Published 21 September 2026 Updated 15 October 2026 Weakness [CWE-444](https://cwe.mitre.org/data/definitions/444.html) ## Vendor fix Update to versions 1.36.10, 1.37.6, 1.38.4, or 1.39.1 or later. Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them. ## References - [https://nvd.nist.gov/vuln/detail/CVE-2026-73548](https://nvd.nist.gov/vuln/detail/CVE-2026-73548) - [https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b](https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b) - [https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c](https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c) - [https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766](https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766) - [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-3vhp-c83q-jqc2](https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2) - [https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361](https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361) - [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) [← All CVEs](https://panop.io/threat-heartbeat/) ## What this record can't tell you - Whether you run the affected software, and where - Whether an attacker can actually reach and exploit it - The misconfigurations that never get a CVE number - What it would cost the business, ranked into what to fix first Panop answers these inside your environment, for this CVE and every other finding. [Book a demo](https://panop.io/demo)