CVE-2026-77804
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.
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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.
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
- Puntuación base: 6.6
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.06%
- Percentil entre todas las CVEs puntuadas: 0
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1203Exploitation for Client Executionexecution90 % - Impacto principal
T1556.004Network Device Authenticationdefense impairment · persistence · credential access85 % - Impacto secundario
T1557.002ARP Cache Poisoningcredential access · collection80 %
TOCTOU en fichero temporal con UI:R (interacción del usuario: aprobar elevación). Impacto: manipulación de autoridades certificadas confiables (T1556.004) y suplantación de identidad en tráfico TLS (T1557.002).
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-367
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-77804",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "security@progress.com",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 6.6,
"attackVector": "LOCAL",
"baseSeverity": "MEDIUM",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N",
"integrityImpact": "HIGH",
"userInteraction": "REQUIRED",
"attackComplexity": "LOW",
"availabilityImpact": "NONE",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.2,
"exploitabilityScore": 1.3
}
]
},
"affected": [
{
"source": "security@progress.com",
"affectedData": [
{
"vendor": "Progress Software",
"product": "Progress® Telerik® Fiddler® Classic",
"versions": [
{
"status": "affected",
"version": "1.0.0",
"lessThan": "6.0.20262.10021",
"versionType": "custom"
}
],
"platforms": [
"Windows"
],
"defaultStatus": "unaffected"
}
]
}
],
"published": "2026-10-05T13:16:54.590",
"references": [
{
"url": "https://docs.telerik.com/fiddler/knowledge-base/kb-security-root-certificate-installation-toctou-cve-2026-77804",
"source": "security@progress.com"
}
],
"vulnStatus": "Received",
"weaknesses": [
{
"type": "Primary",
"source": "security@progress.com",
"description": [
{
"lang": "en",
"value": "CWE-367"
}
]
}
],
"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."
}
],
"lastModified": "2026-10-05T13:16:54.590",
"sourceIdentifier": "security@progress.com"
}