CVE-2026-77805: CWE-347: Improper Verification of Cryptographic Signature in Progress Software Progress® Telerik® Fiddler® Classic
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.
CVSS v3.1
Score 7.9high
Affected software
Progress Software
Progress® Telerik® Fiddler® Classic
pkg:github/progress-software/Telerik-Fiddler-ClassicRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-77805 describes an improper verification of cryptographic signatures in Progress Telerik Fiddler Classic for Windows prior to version 6.0.20262.10021. The application launches external helper tools after verifying their Authenticode signatures only against a broad allow list of publisher name fragments rather than confirming the exact executable matches the shipped version. A local attacker with low privileges can substitute a helper executable with any other validly signed binary from an allowed publisher. If the user launches the affected tool and approves the elevation prompt, the substituted binary executes with Administrator privileges, enabling privilege escalation and unintended code execution.
Potential Impact
Successful exploitation allows a local low-privilege user to escalate privileges to Administrator by substituting helper executables with other validly signed binaries from allowed publishers. This can lead to execution of arbitrary code with elevated privileges. The vulnerability requires user interaction to launch the tool and approve the elevation prompt. There are no known exploits in the wild at this time.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, users should exercise caution when launching external helper tools and carefully verify elevation prompts. Restrict local user permissions to prevent unauthorized replacement of helper executables.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- ProgressSoftware
- Date Reserved
- 2026-08-21T13:37:36.679Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ac3a0512cdf04f65600b118
Added to database: 10/05/2026, 13:04:17 UTC
Last enriched: 10/05/2026, 13:18:13 UTC
Last updated: 10/05/2026, 18:56:34 UTC
Views: 16
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