{"id":"CVE-2026-77802","revision":null,"records":[{"revision":"75d6d0bfbd5d467db1d4a7aa81665ca9","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-77802","aliases":[],"title":"HTTP Request Smuggling Vulnerability in Progress® Telerik® Fiddler® Classic","description":"In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, HTTP request smuggling is possible in the proxy request forwarding component. Requests containing multiple Content-Length headers with conflicting values are forwarded verbatim to the origin server, while Fiddler frames the request body using only the first Content-Length value. A local threat actor with low privileges who is able to send requests through the same Fiddler proxy instance as another user can exploit this desynchronization against a non-RFC-9110-compliant origin server that keeps the connection alive to smuggle an additional request. Because Fiddler returns the server connection to its pipe pool after reading only the first response, the unread smuggled response remains buffered on the socket and is served to the next session that reuses that connection, allowing the attacker to poison responses delivered to other users and to obtain responses intended for them.","state":0,"publishedAt":"2026-10-05T12:38:58.912+00:00","modifiedAt":"2026-10-06T17:51:15.128+00:00","affected":[{"ecosystem":"Vendor product","name":"Progress® Telerik® Fiddler® Classic","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Progress Software\",\n                    \"product\": \"Progress® Telerik® Fiddler® Classic\",\n                    \"platforms\": [\n                        \"Windows\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"status\": \"affected\",\n                            \"version\": \"1.0.0\",\n                            \"lessThan\": \"6.0.20262.10021\",\n                            \"versionType\": \"custom\"\n                        }\n                    ],\n                    \"defaultStatus\": \"unaffected\"\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N","score":6.3,"severity":"MEDIUM"}],"references":["https://docs.telerik.com/fiddler/knowledge-base/kb-security-http-request-smuggling-cve-2026-77802"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-77802","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-77802","identifiers":["CVE-2026-77802"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-f0a4583a21084daab8e852bf5d038b99","complete":false,"records":13759,"lastAttemptAt":"2026-11-11T14:09:33.1310684+00:00","lastSuccessAt":"2026-11-11T14:09:33.127+00:00","error":null,"lastVerifiedAt":"2026-11-11T14:09:33.127+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13569,"expectedIdentifiers":13813,"failedIdentifiers":0},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. Not a global EPSS backfill.","generation":"2026-11-11T13:57:33.6529555+00:00","complete":true,"records":1097,"lastAttemptAt":"2026-11-11T13:57:33.6529555+00:00","lastSuccessAt":"2026-11-11T13:57:33.8250558+00:00","error":null,"lastVerifiedAt":"2026-11-11T13:57:33.8250561+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"nvd","scope":"Rolling NVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global NVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-11785b13898646a1917b06b09d2df4a4","complete":true,"records":13753,"lastAttemptAt":"2026-11-11T13:57:34.9144807+00:00","lastSuccessAt":"2026-11-11T13:57:34.909+00:00","error":null,"lastVerifiedAt":"2026-11-11T13:57:34.909+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13813,"expectedIdentifiers":13813,"failedIdentifiers":0},{"source":"osv:Go","scope":"Complete OSV Go ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"go-3562b6c78fd1bd0f0b55daf66a0926ae24f65e462df7f6d928caad458fc696bf","complete":true,"records":9947,"lastAttemptAt":"2026-11-11T13:57:33.3950468+00:00","lastSuccessAt":"2026-11-11T04:27:43.6877707+00:00","error":null,"lastVerifiedAt":"2026-11-11T13:57:33.3950468+00:00","snapshotPublishedAt":"2026-11-11T03:32:46+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:NuGet","scope":"Complete OSV NuGet ecosystem archive, including GitHub Advisory Database records; NuGet version matching only","generation":"nuget-456002455e0ab94bb92c95476d4e6d175c104cd594749982afd96c893728ecbc","complete":true,"records":2010,"lastAttemptAt":"2026-11-11T13:57:32.9057946+00:00","lastSuccessAt":"2026-11-11T02:36:58.1276999+00:00","error":null,"lastVerifiedAt":"2026-11-11T13:57:32.9057946+00:00","snapshotPublishedAt":"2026-11-11T01:17:51+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:crates.io","scope":"Complete OSV crates.io ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"crates.io-baa8362b4daf9e5f39d5563775a55935e7b442c0735d33274a921579ce4a0d66","complete":true,"records":3093,"lastAttemptAt":"2026-11-11T13:57:33.6132068+00:00","lastSuccessAt":"2026-11-11T13:00:02.5446881+00:00","error":null,"lastVerifiedAt":"2026-11-11T13:57:33.6132068+00:00","snapshotPublishedAt":"2026-11-11T12:47:47+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:npm","scope":"Complete OSV npm ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"npm-10cb353ca77c2a8069d6892d1d394d936b12c0add3c8749e2a1a03a1c5d50426","complete":true,"records":231666,"lastAttemptAt":"2026-11-11T13:57:33.0989698+00:00","lastSuccessAt":"2026-11-11T12:59:55.8981437+00:00","error":null,"lastVerifiedAt":"2026-11-11T13:57:33.0989698+00:00","snapshotPublishedAt":"2026-11-11T12:32:53+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null}]}