CVE-2026-86158

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

State: Published
Severity: 7.7 High
Published: Sep 29, 2026
Updated: Sep 30, 2026
Reserved: Sep 5, 2026

Description

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.

Scores

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

Weaknesses

CWE-306 Missing Authentication for Critical Function

Affected Products

Product	Versions
Progress® Telerik® Fiddler® EverywhereProgress Software	1.0.0 to before 8.2.0Affected

References

https://www.telerik.com/fiddler/fiddler-everywhere/documentation/knowledge-base/kb-security-missing-authentication-for-critical-function-cve-2026-86158vendor-advisory

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