CVE-2026-86158 PUBLISHED

Missing Authentication in the local .NET backend of Progress Telerik Fiddler Everywhere

Assigner: ProgressSoftware
Reserved: 05.09.2026 Published: 29.09.2026 Updated: 29.09.2026

Missing authentication in the local .NET backend (Fiddler.WebUi) of Progress Software Fiddler Everywhere 8.0.2 allows a local unauthenticated attacker to mint OAuth tokens and read the machine-in-the-middle root certificate through an unauthenticated localhost HTTP and SignalR RPC channel.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS Score: 7.7

Attack Vector	Local	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Progress Software
Product	Progress® Telerik® Fiddler® Everywhere
Versions	Default: unaffected affected from 1.0.0 to 8.2.0 (excl.)

Credits

whizarre finder

References

https://www.telerik.com/fiddler/fiddler-everywhere/documentation/knowledge-base/kb-security-exposed-dangerous-method-or-function-cve-2026-aaaaa

Problem Types

CWE-306: Missing Authentication for Critical Function CWE

Impacts

Authentication Bypass