{"id":"CVE-2026-77803","revision":"6a96a1a4bc7c4265af730613210775b7","records":[{"revision":"6a96a1a4bc7c4265af730613210775b7","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-77803","aliases":[],"title":"Front-end Desynchronization Vulnerability in Progress® Telerik® Fiddler® Classic","description":"In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, front-end request desynchronization is possible in the proxy request forwarding component. A request that contains both a Content-Length and a Transfer-Encoding header is forwarded with both headers present, while Fiddler frames the body using Transfer-Encoding only. The remaining bytes on the reused client connection are then parsed as a separate pipelined request, so a local threat actor with low privileges can cause a single malformed request to be split into two requests forwarded to the origin server and receive an additional smuggled response, without requiring a vulnerable server.","state":0,"publishedAt":"2026-10-05T12:39:36.806+00:00","modifiedAt":"2026-10-06T17:50:34.935+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:L/I:L/A:N","score":3.6,"severity":"LOW"}],"references":["https://docs.telerik.com/fiddler/knowledge-base/kb-security-front-end-desynchronization-cve-2026-77803"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-77803","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-77803","identifiers":["CVE-2026-77803"]},"retained":false,"historicalAffected":[]}],"coverage":[]}