Description
In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, the integrity check applied to the external helper tools launched by the application is insufficient. Before executing a helper tool, the application only verifies that the file carries a valid Authenticode signature whose certificate subject name matches a broad allow list of publisher name fragments, rather than verifying that the file is the specific executable shipped with that version of the product. A local threat actor with low privileges who replaces one of these helper executables with any other validly signed binary from an allow-listed publisher can cause the substituted binary to be executed by the application, including with Administrator privileges for the tools that request elevation, resulting in privilege escalation and execution of unintended code. Successful exploitation requires the user to launch the affected external tool and to approve the elevation prompt without noticing that it refers to a different executable.
Published: 2026-10-05
Score: 7.9 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

Vendor Workaround

Carefully review every User Account Control elevation prompt raised by Fiddler Classic and confirm that it refers to the expected executable before approving it. Alternatively, avoid launching external tools from the Fiddler Classic application, such as the Windows 8 Loopback Exemptions tool or the machine store certificate trust tool.

Tracking

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Advisories

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History

Mon, 05 Oct 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Mon, 05 Oct 2026 13:00:00 +0000

Type Values Removed Values Added
Description In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, the integrity check applied to the external helper tools launched by the application is insufficient. Before executing a helper tool, the application only verifies that the file carries a valid Authenticode signature whose certificate subject name matches a broad allow list of publisher name fragments, rather than verifying that the file is the specific executable shipped with that version of the product. A local threat actor with low privileges who replaces one of these helper executables with any other validly signed binary from an allow-listed publisher can cause the substituted binary to be executed by the application, including with Administrator privileges for the tools that request elevation, resulting in privilege escalation and execution of unintended code. Successful exploitation requires the user to launch the affected external tool and to approve the elevation prompt without noticing that it refers to a different executable.
Title Weak Executable Signature Verification Vulnerability in Progress® Telerik® Fiddler® Classic
Weaknesses CWE-347
References
Metrics cvssV3_1

{'score': 7.9, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N'}


Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: ProgressSoftware

Published:

Updated: 2026-10-05T15:26:04.778Z

Reserved: 2026-08-21T13:37:36.679Z

Link: CVE-2026-77805

cve-icon Vulnrichment

Updated: 2026-10-05T13:57:07.714Z

cve-icon NVD

Status : Received

Published: 2026-10-05T13:16:54.740

Modified: 2026-10-05T16:17:16.293

Link: CVE-2026-77805

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-05T15:15:08Z

Weaknesses