{"attribution":"This product uses data from the NVD API but is not endorsed or certified by the NVD.","cve":{"id":"CVE-2026-73548","sourceIdentifier":"security-advisories@github.com","published":"2026-09-21T20:17:28.397","lastModified":"2026-10-05T14:19:45.960","vulnStatus":"Analyzed","cveTags":[],"descriptions":[{"lang":"en","value":"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 forwards data for a configured non-WebSocket HTTP upgrade before the upstream accepts the upgrade. An unauthenticated HTTP/2 client can place a complete HTTP/1.1 request in extended CONNECT data; Envoy downgrades the request, writes the data unframed to a keep-alive HTTP/1.1 upstream, and returns the socket to the shared pool while the smuggled response remains queued. A different downstream client can then receive the attacker's response. The relevant scope boundary is that webSocket upgrades, plain CONNECT, disabled backend keep-alive, per-downstream pools, and max_requests_per_connection set to 1 are not affected by the demonstrated path. This issue is fixed in versions 1.36.10, 1.37.6, 1.38.4, and 1.39.1."}],"affected":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"envoyproxy","product":"envoy","versions":[{"version":"\u003c 1.36.10","status":"affected"},{"version":"\u003e= 1.37.0, \u003c 1.37.6","status":"affected"},{"version":"\u003e= 1.38.0, \u003c 1.38.4","status":"affected"},{"version":"\u003e= 1.39.0, \u003c 1.39.1","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"NONE"},"exploitabilityScore":3.9,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-09-24T22:34:49.061262Z","id":"CVE-2026-73548","options":[{"exploitation":"poc"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-444"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*","versionEndExcluding":"1.36.10","matchCriteriaId":"6A420B14-9ADA-4F6B-ACAA-3045E8690F04"},{"vulnerable":true,"criteria":"cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*","versionStartIncluding":"1.37.0","versionEndExcluding":"1.37.6","matchCriteriaId":"1AD376F3-22D7-4BFB-B00C-BD68F464436F"},{"vulnerable":true,"criteria":"cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*","versionStartIncluding":"1.38.0","versionEndExcluding":"1.38.4","matchCriteriaId":"840E030F-8746-4DBD-87C0-5DF7896294CC"},{"vulnerable":true,"criteria":"cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*","versionStartIncluding":"1.39.0","versionEndExcluding":"1.39.1","matchCriteriaId":"B5C1C594-8142-4F51-BE50-1AF50FD07129"}]}]}],"references":[{"url":"https://github.com/envoyproxy/envoy/commit/309855626966cff176155c821043ed3b44671361","source":"security-advisories@github.com","tags":["Patch"]},{"url":"https://github.com/envoyproxy/envoy/commit/3c7998545a9c9fb3933a4bc1907d92f0e752bc2b","source":"security-advisories@github.com","tags":["Patch"]},{"url":"https://github.com/envoyproxy/envoy/commit/4633b8cce3d15b8734eefe232e30c12b0140b91c","source":"security-advisories@github.com","tags":["Patch"]},{"url":"https://github.com/envoyproxy/envoy/commit/bd6711f2617658e28dfa3df3dace6bfe3cfc0766","source":"security-advisories@github.com","tags":["Patch"]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.36.10","source":"security-advisories@github.com","tags":["Release Notes"]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.37.6","source":"security-advisories@github.com","tags":["Release Notes"]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.38.4","source":"security-advisories@github.com","tags":["Release Notes"]},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.39.1","source":"security-advisories@github.com","tags":["Release Notes"]},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2","source":"security-advisories@github.com","tags":["Exploit","Vendor Advisory"]},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-3vhp-c83q-jqc2","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":["Exploit","Vendor Advisory"]}]}}