{"schemaVersion":3,"id":"CVE-2026-77804","aliases":[],"status":"published","duplicateOf":null,"title":null,"description":"In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, a time-of-check time-of-use (TOCTOU) race condition exists in the installation of the HTTPS interception root certificate into the Local Computer certificate store. Fiddler writes the certificate to a temporary file in a user-writable location and then launches the external TrustCert helper application, which elevates and imports the certificate from that file. A local threat actor with low privileges who replaces the temporary file between the time it is written and the time the elevated helper reads it can cause an attacker-supplied root certificate to be installed in the Local Computer Trusted Root Certification Authorities store, enabling subsequent interception and modification of TLS-protected traffic on the machine. Successful exploitation requires the user to initiate the certificate trust operation and approve the elevation prompt.","dates":{"published":"2026-10-05T12:40:26.811Z","modified":"2026-10-06T17:49:23.338Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":6.6,"severity":"medium","version":"3.1","versionLabel":"v3.1","source":"CVE.org","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":6.6,"severity":"medium","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":6.6,"severity":"medium","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00058,"percentile":0.00004,"severity":"low","asOf":"2026-10-20T00:00:00.000Z","change":{"pp":null,"baselineDate":null,"baselineScore":null},"history":[{"date":"2026-10-06T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00058,"percentile":0.00004}],"last30":[{"date":"2026-10-06T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00058,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00058,"percentile":0.00004}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[],"exploitCount":0,"weaknesses":[{"id":"CWE-367","name":"Time-of-check Time-of-use (TOCTOU) Race Condition","description":"The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.","type":"weakness","status":"Incomplete","abstraction":"Base","likelihoodOfExploit":"Medium","url":"https://cwe.mitre.org/data/definitions/367.html"}],"affected":[{"vendor":"progress software","product":"progress® telerik® fiddler® classic","name":"Progress® Telerik® Fiddler® Classic","label":"progress® telerik® fiddler® classic","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"≥ 1.0.0, < 6.0.20262.10021","noFixRecorded":false,"fixedIn":null}],"versionsText":"≥ 1.0.0, < 6.0.20262.10021","eol":null,"hubHref":"/vendor/progress_software/progress_telerik_fiddler_classic"}],"affectedCount":1,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://docs.telerik.com/fiddler/knowledge-base/kb-security-root-certificate-installation-toctou-cve-2026-77804","label":"docs.telerik.com/fiddler/…","hostname":"docs.telerik.com","tags":["Vendor Advisory"]}],"lineage":{"upstream":[],"downstream":[],"duplicates":[],"related":[]},"timeline":[{"kind":"published","date":"2026-10-05T12:40:26.811Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-10-06T17:49:23.338Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":26,"level":"medium","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-21T04:02:38.575Z","stale":false,"partial":false}}