{"id":"CVE-2026-77804","state":"PUBLISHED","title":"Time-of-check Time-of-use (TOCTOU) Race Condition in Root Certificate Installation in Progress® Telerik® Fiddler® Classic","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.","publishedAt":"2026-10-05T12:40:26.811Z","updatedAt":"2026-10-06T17:49:23.338Z","severity":{"score":6.6,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N","source":"ProgressSoftware"},"assigner":"ProgressSoftware","products":["Progress Software Progress® Telerik® Fiddler® Classic"],"affected":[{"vendor":"Progress Software","product":"Progress® Telerik® Fiddler® Classic","defaultStatus":"unaffected","versions":[{"version":"1.0.0","status":"affected","lessThan":"6.0.20262.10021","versionType":"custom"}],"platforms":["Windows"]}],"references":["https://docs.telerik.com/fiddler/knowledge-base/kb-security-root-certificate-installation-toctou-cve-2026-77804"],"weaknesses":["CWE-367"],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/77xxx/CVE-2026-77804.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-77804","state":"PUBLISHED","datePublished":"2026-10-05T12:40:26.811Z","dateUpdated":"2026-10-06T17:49:23.338Z","assignerShortName":"ProgressSoftware","assignerOrgId":"f9fea0b6-671e-4eea-8fde-31911902ae05","dateReserved":"2026-08-21T13:37:35.057Z"},"containers":{"cna":{"title":"Time-of-check Time-of-use (TOCTOU) Race Condition in Root Certificate Installation in Progress® Telerik® Fiddler® Classic","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Progress Software","product":"Progress® Telerik® Fiddler® Classic","defaultStatus":"unaffected","versions":[{"version":"1.0.0","status":"affected","lessThan":"6.0.20262.10021","versionType":"custom"}],"platforms":["Windows"]}],"references":[{"url":"https://docs.telerik.com/fiddler/knowledge-base/kb-security-root-certificate-installation-toctou-cve-2026-77804","tags":["vendor-advisory"]}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV3_1":{"version":"3.1","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"NONE","baseSeverity":"MEDIUM","baseScore":6.6,"vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-367","lang":"en","description":"CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition","type":"CWE"}]}],"providerMetadata":{"shortName":"ProgressSoftware","orgId":"f9fea0b6-671e-4eea-8fde-31911902ae05","dateUpdated":"2026-10-05T12:40:26.811Z"},"impacts":[{"capecId":"CAPEC-29","descriptions":[{"lang":"en","value":"CAPEC-29 Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions"}]}],"workarounds":[{"lang":"en","value":"Trust the Fiddler Classic certificate only in the Current User certificate store. When the application asks to install the certificate in the Local Computer (local machine) store, choose No. If a machine-wide trust is required, export the certificate to a file and import that file into the Local Computer Trusted Root Certification Authorities store manually.","supportingMedia":[{"type":"text/html","base64":false,"value":"<div>Trust the Fiddler Classic certificate only in the <b>Current User</b> certificate store. When the application asks to install the certificate in the <b>Local Computer</b> (local machine) store, choose <b>No</b>. If a machine-wide trust is required, export the certificate to a file and import that file into the Local Computer Trusted Root Certification Authorities store manually.</div>"}]}],"credits":[{"lang":"en","value":"NATO Cyber Security Centre (NCSC)","type":"finder"}],"source":{"discovery":"EXTERNAL"},"x_generator":{"engine":"Vulnogram 0.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-06T17:49:19.748248Z","id":"CVE-2026-77804","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-06T17:49:23.338Z"}}]}}}