CVE-2026-77805Weak Executable Signature Verification Vulnerability in Progress® Telerik® Fiddler® Classic

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

7.9 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Weakness (CWE)

CWE-347

Known exploited

Not in CISA's KEV catalog

EPSS (exploitation in the next 30 days)

0.06% (percentile 0)

Assigned by

ProgressSoftware

NVD analysis

Awaiting Analysis

Record last updated

Oct 5, 2026

First seen by InfoSec Signals

Oct 9, 2026

The CVE record on cve.org · NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.