Missing Authentication in the local .NET backend of Progress Telerik Fiddler Everywhere (CVE-2026-86158) | HOL Guard CVE

High · CVSS 7.7CVE-2026-86158

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

Answer in brief

CVE-2026-86158 records a High severity (CVSS 7.7) vulnerability in Missing Authentication in the local .NET backend of Progress Telerik Fiddler Everywhere. The current sources do not mark it as known exploited. The current feed maps Progress Software/Progress® Telerik® Fiddler® Everywhere (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 29, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 29, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Progress Software/Progress® Telerik® Fiddler® Everywhere (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Progress Software/Progress® Telerik® Fiddler® Everywheregeneric	>=1.0.0 <8.2.0	8.2.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for Progress Software/Progress® Telerik® Fiddler® Everywhere.
Review the reported fix. Update Progress Software/Progress® Telerik® Fiddler® Everywhere to 8.2.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 29, 2026

Sources and claim methodology

Source referencetelerik.com

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.