CVE-2026-77805 Weak Executable Signature Verification Vulnerability in Progress® Telerik® Fiddler® Classic
Local attackers can bypass signature checks to execute arbitrary signed binaries with elevated privileges, requiring user interaction to approve elevation prompts.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-77805?
CVE-2026-77805 is a high-severity vulnerability in Progress® Telerik® Fiddler® Classic, published on 5 Oct 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-347
Which versions are affected by CVE-2026-77805?
How do I fix CVE-2026-77805?
No fix has been published for CVE-2026-77805 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-77805 being exploited?
There is no known exploitation of CVE-2026-77805 in the wild and no public exploit code.
Sources
Also known as GHSA-mpj7-wp32-q53h.