Authentication Bypass in Progress Software Fiddler Everywhere
CVE-2026-86158

7.7HIGH

Key Information:

Vendor

Progress Software
Status
Progress® Telerik® Fiddler® Everywhere
Vendor
CVE Published:
29 September 2026

What is CVE-2026-86158?

A significant authentication bypass vulnerability exists in the local .NET backend of Progress Software's Fiddler Everywhere version 8.0.2. This flaw enables local unauthenticated attackers to exploit the unsecured localhost HTTP and SignalR RPC channel, effectively minting OAuth tokens. Additionally, the absence of proper authentication controls allows access to the machine-in-the-middle root certificate, potentially facilitating further attacks.

Affected Version(s)

Progress® Telerik® Fiddler® Everywhere 1.0.0 < 8.2.0

References

https://www.telerik.com/fiddler/fiddler-everywhere/docume...
vendor-advisory

CVSS V3.1

Score:
7.7
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Local
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

whizarre
.