---
id: CVE-2026-86158
title: >-
  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 un…
summary: >-
  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 un…
severity: high
cvss: 7.7
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'
cwe:
  - CWE-306
vendor: Progress Software
product: Progress® Telerik® Fiddler® Everywhere
affected:
  - progress_telerik_fiddler_everywhere >= 1.0.0 < 8.2.0
published: '2026-09-29'
updated: '2026-09-29'
sourceUpdated: '2026-09-29T07:16:35.520'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-86158'
references:
  - url: >-
      https://www.telerik.com/fiddler/fiddler-everywhere/documentation/knowledge-base/kb-security-exposed-dangerous-method-or-function-cve-2026-aaaaa
    label: security@progress.com
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-29T07:29:26.132Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.