{"id":"CVE-2026-73550","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-73550","generatedAt":"2026-10-28T03:58:39.963Z","title":"The discarded value bypasses saveHeader, so its bytes and count are not charged against request header limits.","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.","published":"2026-09-21T20:17:29.000Z","lastModified":"2026-10-05T14:07:46.000Z","status":"Analyzed","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-401"],"affected":["envoyproxy/envoy"],"epss":{"score":0.00552,"percentile":0.45954,"date":"2026-10-27","history":[{"date":"2026-09-22","score":0.00879,"percentile":0.57552}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.55%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-09-21T20:17:29.000Z","detail":{"score":"7.5","severity":"HIGH","publishedAt":"2026-09-21T20:17:28.733Z"},"summary":"New CVE, high severity (CVSS 7.5)."}],"references":[{"url":"https://github.com/envoyproxy/envoy/commit/0910997f70e91d2d20c329bb507bfce44ce01f80","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/commit/1fec994c868df008cdd4ae285aab58a196fd31f2","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/commit/3fd0ffee7ac87adf3bc6e421656bb96310512300","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/commit/fc75d8e35b0d11acbae18b63a0bd96e32e84f61b","tags":["Patch"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.36.10","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.37.6","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.38.4","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/releases/tag/v1.39.1","tags":["Release Notes"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh","tags":["Exploit","Vendor Advisory"],"source":"security-advisories@github.com"},{"url":"https://github.com/envoyproxy/envoy/security/advisories/GHSA-qgf6-qvhw-4hvh","tags":["Exploit","Vendor Advisory"],"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-73550","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}