CVE-2026-77803
LowCVSS 3.6Exploitation Probability (EPSS)
Low risk0th percentile - higher than 0% of all known CVEs
Summary
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 containing both Content-Length and Transfer-Encoding headers is forwarded with both headers present, while Fiddler frames the body using Transfer-Encoding only. The remaining bytes on the reused client connection are then parsed as a separate pipelined request, so a local threat actor with low privileges can cause a single malformed request to be split into two requests forwarded to the origin server and receive an additional smuggled response, without requiring a vulnerable server.
Risk Assessment
The risk includes the possibility of request smuggling attacks by a local user, which could lead to unauthorized data access or response manipulation. Low privileges are required, but the attack can be performed remotely.
Recommendation
It is recommended to upgrade Fiddler Classic to version v6.0.20262.10021 or later. Also restrict local access to systems running Fiddler.
Related vulnerabilities
- CVE-2026-118235Critical
The SimpleForm plugin for WordPress (versions up to and including 3.10.2) is vulnerable to arbitrary file upload via the handle_upload function. Missing a server-side file key allowlist and pre-sanitization extension derivation allows a trailing-dot filename to bypass all extension and MIME validation, enabling unauthenticated attackers to upload executable files and achieve remote code execution. The only access control is a nonce printed into every public form's data-nonce attribute, trivially obtainable by any unauthenticated visitor.
- CVE-2026-103882Critical
The Acadlix LMS plugin for WordPress (versions up to and including 1.1.9) is vulnerable to arbitrary file deletion due to insufficient file path validation in the post_delete_assessment_file_by_id function. Authenticated attackers with subscriber-level access or higher can delete arbitrary files on the server, potentially leading to remote code execution when critical files such as wp-config.php are deleted. The route's permission callback only verifies a generic wp_rest nonce emitted in the public acadlixOptions JavaScript object on every frontend page, effectively reducing the authentication requirement to unauthenticated.
- CVE-2026-119096Critical
The Uncanny Toolkit for LearnDash plugin for WordPress (up to 3.8.2) is vulnerable to Authentication Bypass via the 'email' parameter in uo_login_action(). A parser-differential flaw allows skipping account verification by using a raw string for lookup and a sanitized string for login. This lets unauthenticated attackers log in to unverified or suspended accounts if they know the credentials.
- CVE-2026-116512Critical
The Project Manager – AI Powered Project Management plugin for WordPress (up to 4.1.1) is vulnerable to Remote Code Execution via the 'id' parameter. The unsanitized value is concatenated into a validation rule string and then invoked as a dynamic PHP function without allowlist checks. This allows unauthenticated attackers to execute code on the server.
- CVE-2026-89270Critical
The Popup Builder plugin for WordPress in versions up to and including 4.4.5 does not properly verify that a user is authorized to perform an action. An unauthenticated attacker can trash all published popups on the site with a single GET request, amplified by a second flaw in SGPopup::find() that causes the trash branch to fire against every popup simultaneously.
- CVE-2026-116557Critical
The WP Booking System – Booking Calendar plugin for WordPress in versions up to and including 2.1.0.5 lacks a capability check in the wpbs_action_ajax_calendar_remove_note() function. An authenticated attacker with Subscriber-level access or above can delete arbitrary calendar notes belonging to any calendar.
- CVE-2026-109220Critical
The PDF Invoice for WooCommerce + Drag and Drop Template Builder plugin in versions up to and including 7.1.1 is vulnerable to PHP Object Injection via the 'customer_note' parameter. The checkout field is insufficiently sanitized and passed to unserialize() without validation, allowing unauthenticated attackers to execute code on the server.
- CVE-2026-117656Critical
The pow-auth Assent library's Sign in with Apple strategy trusts the browser-supplied 'user' parameter, which the client controls. That parameter is merged over the verified ID token claims, allowing an unauthenticated remote attacker to impersonate another user. Affects versions from 0.1.25 before 0.3.2.
- CVE-2026-63377Critical
In TAKO AI Agent for Okta prior to 3.0.1-beta, the POST /api/auth/setup endpoint allows an unauthenticated network attacker to create the first administrator account before the legitimate owner completes initial setup. The initial_setup function checks only the is_setup flag and requires no authentication, bootstrap token, or network restriction, and the default configuration listens on 0.0.0.0:8001.
- CVE-2026-62863Critical
MoLing in SSE mode (started with -l) does not authenticate requests to the /sse and /message endpoints, and the mcp-go dependency sets Access-Control-Allow-Origin: *. A malicious web page can open a cross-origin EventSource to /sse, read the sessionId, and send unauthorized MCP tool calls via /message, potentially leading to file read/write or command execution. The issue is fixed in version 0.5.0.
Original NVD description (English source)
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, while Fiddler frames the body using Transfer-Encoding only. The remaining bytes on the reused client connection are then parsed as a separate pipelined request, so a local threat actor with low privileges can cause a single malformed request to be split into two requests forwarded to the origin server and receive an additional smuggled response, without requiring a vulnerable server.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

