CVE-2026-77802 HTTP Request Smuggling Vulnerability in Progress® Telerik® Fiddler® Classic

In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, HTTP request smuggling is possible in the proxy request forwarding component. Requests containing multiple Content-Length headers with conflicting values are forwarded verbatim to the origin server, while...

PT-2026-105990

In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, the integrity check applied to the external helper tools launched by the application is insufficient. Before executing a helper tool, the application only verifies that the file carries a valid Authenticode...

CVE-2026-77804: Time-of-check Time-of-use (TOCTOU) Race Condition

In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, a time-of-check time-of-use TOCTOU race condition exists in the installation of the HTTPS interception root certificate into the Local Computer certificate store. Fiddler writes the certificate to a temporary...

PT-2026-105989

Name of the Vulnerable Software and Affected Versions Progress Telerik Fiddler Classic versions prior to 6.0.20262.10021 Description A time-of-check time-of-use TOCTOU race condition occurs during the installation of the HTTPS interception root certificate into the Local Computer certificate stor...

PT-2026-105987

Name of the Vulnerable Software and Affected Versions Progress Telerik Fiddler Classic for Windows versions prior to 6.0.20262.10021 Description HTTP request smuggling is possible in the proxy request forwarding component. This occurs when requests containing multiple Content-Length headers with...

CVE-2026-77802: Inconsistent Interpretation of HTTP Requests

In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, HTTP request smuggling is possible in the proxy request forwarding component. Requests containing multiple Content-Length headers with conflicting values are forwarded verbatim to the origin server, while...

CVE-2026-77805: Improper Verification of Cryptographic Signature

In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, the integrity check applied to the external helper tools launched by the application is insufficient. Before executing a helper tool, the application only verifies that the file carries a valid Authenticode...

KLA91318 SB vulnerability in Telerik Fiddler

Multiple vulnerabilities were found in Telerik Fiddler. Malicious users can exploit these vulnerabilities to bypass security restrictions, gain privileges. Below is a complete list of vulnerabilities: 1. Security vulnerability can be exploited to bypass security restrictions. 2. An elevation of...

PT-2026-105988

Name of the Vulnerable Software and Affected Versions Progress Telerik Fiddler Classic for Windows versions prior to 6.0.20262.10021 Description Front-end request desynchronization is possible in the proxy request forwarding component. When a request contains both Content-Length and...

CVE-2026-77803: Inconsistent Interpretation of HTTP Requests

In Progress® Telerik® Fiddler® Classic for Windows, versions prior to v6.0.20262.10021, front-end request desynchronization is possible in the proxy request forwarding component. A request that contains both a Content-Length and a Transfer-Encoding header is forwarded with both headers present,...

CVE-2026-86157

Exposure of privileged IPC functionality in Progress Telerik Fiddler Everywhere before version 8.2.0 allows a local, low-privileged attacker who can modify application launch parameters and persuade a user to start the application to replace the application UI or settings with attacker-controlled...

CVE-2026-86158

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...

CVE-2026-86158 Missing Authentication in the local .NET backend of Progress Telerik Fiddler Everywhere

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...

CVE-2026-86158 Missing Authentication in the local .NET backend of Progress Telerik Fiddler Everywhere

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...

CVE-2026-86158

Progress Software Fiddler Everywhere 8.0.2 contains a vulnerability due to missing authentication in its local .NET backend (Fiddler.WebUi ). A local unauthenticated attacker can exploit unauthenticated localhost HTTP and SignalR RPC channels to mint OAuth tokens and read the machine-in-the-middl...

EUVD-2026-88649

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...

CVE-2026-86157 Exposure of Privileged IPC Functionality in Progress Telerik Fiddler Everywhere

Exposure of privileged IPC functionality in Progress Telerik Fiddler Everywhere before version 8.2.0 allows a local, low-privileged attacker who can modify application launch parameters and persuade a user to start the application to replace the application UI or settings with attacker-controlled...

CVE-2026-86157

Progress Telerik Fiddler Everywhere versions prior to 8.2.0 are vulnerable to the exposure of privileged IPC functionality . A local, low-privileged attacker who can modify application launch parameters and influence a user to start the application can replace the UI or settings with attacker-con...

EUVD-2026-88648

Exposure of privileged IPC functionality in Progress Telerik Fiddler Everywhere before version 8.2.0 allows a local, low-privileged attacker who can modify application launch parameters and persuade a user to start the application to replace the application UI or settings with attacker-controlled...

CVE-2026-86157 Exposure of Privileged IPC Functionality in Progress Telerik Fiddler Everywhere

Exposure of privileged IPC functionality in Progress Telerik Fiddler Everywhere before version 8.2.0 allows a local, low-privileged attacker who can modify application launch parameters and persuade a user to start the application to replace the application UI or settings with attacker-controlled...