CVE-2026-77804

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-77804", "assignerOrgId": "f9fea0b6-671e-4eea-8fde-31911902ae05", "state": "PUBLISHED", "assignerShortName": "ProgressSoftware", "dateReserved": "2026-08-21T13:37:35.057Z", "datePublished": "2026-10-05T12:40:26.811Z", "dateUpdated": "2026-10-06T17:49:23.338Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "f9fea0b6-671e-4eea-8fde-31911902ae05", "shortName": "ProgressSoftware", "dateUpdated": "2026-10-05T12:40:26.811Z"}, "title": "Time-of-check Time-of-use (TOCTOU) Race Condition in Root Certificate Installation in Progress\u00ae Telerik\u00ae Fiddler\u00ae Classic", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-367", "description": "CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition", "type": "CWE"}]}], "impacts": [{"capecId": "CAPEC-29", "descriptions": [{"lang": "en", "value": "CAPEC-29 Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions"}]}], "affected": [{"vendor": "Progress Software", "product": "Progress\u00ae Telerik\u00ae Fiddler\u00ae Classic", "platforms": ["Windows"], "versions": [{"status": "affected", "version": "1.0.0", "lessThan": "6.0.20262.10021", "versionType": "custom"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "In Progress\u00ae Telerik\u00ae Fiddler\u00ae 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.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "In Progress\u00ae Telerik\u00ae Fiddler\u00ae 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."}]}], "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"}}], "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": [{"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"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-06T17:49:23.338Z"}}]}}

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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", "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>", "base64": false}]}], "x_generator": {"engine": "Vulnogram 0.2.0"}, "descriptions": [{"lang": "en", "value": "In Progress\u00ae Telerik\u00ae Fiddler\u00ae 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.", "supportingMedia": [{"type": "text/html", "value": "In Progress\u00ae Telerik\u00ae Fiddler\u00ae 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. 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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "platforms": ["Windows"], "product": "Progress\u00ae Telerik\u00ae Fiddler\u00ae Classic", "vendor": "Progress Software", "versions": [{"lessThan": "6.0.20262.10021", "status": "affected", "version": "1.0.0", "versionType": "custom"}]}], "source": "security@progress.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In Progress\u00ae Telerik\u00ae Fiddler\u00ae 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."}], "id": "CVE-2026-77804", "lastModified": "2026-10-06T18:16:56.393", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "NONE", "baseScore": 6.6, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 1.3, "impactScore": 5.2, "source": "security@progress.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-77804", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-06T17:49:19.748248Z", "version": "2.0.3"}}]}, "published": "2026-10-05T13:16:54.590", "references": [{"source": "security@progress.com", "url": "https://docs.telerik.com/fiddler/knowledge-base/kb-security-root-certificate-installation-toctou-cve-2026-77804"}], "sourceIdentifier": "security@progress.com", "vulnStatus": "Awaiting Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-367"}], "source": "security@progress.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": ["windows"], "status": "affected", "versions": {"scheme": "generic", "value": "[1.0.0,6.0.20262.10021)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "manual", "scores": [{"score": 100.0, "source": "manual"}]}, "original": {"product": "Progress\u00ae Telerik\u00ae Fiddler\u00ae Classic", "source": "cna", "vendor": "Progress Software"}, "product": "progress_telerik_fiddler_classic", "vendor": "progress_software"}], "created": "2026-10-05T14:45:20.666077+00:00", "updated": "2026-10-06T20:57:46.523449+00:00", "vendors": ["progress_software", "progress_software$PRODUCT$progress_telerik_fiddler_classic"]}