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-2026-28336Critical
SolarWinds Dameware is affected by a command injection vulnerability that could lead to compromise of the remotely controlled host. Authentication is required.
- CVE-2026-109593Critical
An unauthenticated attacker with network access to SonicWall GMS 9.5.2 and earlier may be able to read internal GMS files, potentially exposing sensitive information.
- CVE-2026-121260Critical
Ziroom ZHOME A0101 1.0.1.0 Build 202004151405 contains a flaw in the loadstring function of usr/lib/lua/luci/controller/api/zrUsb.lua (Lua Handler component). The manipulation causes code injection and can be exploited remotely. The exploit has been published and may be used; the vendor did not respond to the disclosure.
- CVE-2026-118527MediumActively exploited
Use of predictable filenames in Ivanti Connect Secure before versions 25.1.1.3 and 22.8R2.6 allows a remote authenticated attacker to upload files with attacker-controlled content to a known location on disk.
- CVE-2026-89292Critical
In Eclipse Mnestix Browser versions 1.6.0 up to but excluding 2.3.0, an unauthenticated attacker could exfiltrate the MNESTIX_BACKEND_API_KEY for all configured Infrastructures.
- CVE-2026-4052Critical
This issue only impacts deployments where WSO2 Identity Server is configured as a Resident Key Manager with database sharing. In such environments, a self-registered user may gain access to the System REST APIs of WSO2 API Manager by obtaining a token from the WSO2 Identity Server token endpoint.
- CVE-2026-13594Critical
Zoho Corporation's ManageEngine Log360 and EventLog Analyzer versions 13062 and below are vulnerable to an issue that could allow an adversary to gain unauthorized access to the product.
- CVE-2026-120534Critical
The Advanced Custom Fields: Extended PRO plugin for WordPress is vulnerable to Limited Code Injection in all versions up to, and including, 0.9.2.6 via the render_field function. Insufficient validation of form configuration parameters allows unauthenticated attackers to call arbitrary WordPress functions with controlled arguments.
- CVE-2026-120518Critical
The BuddyPress XProfile Image Field plugin for WordPress is vulnerable to arbitrary file deletion in all versions up to, and including, 3.1.0. The bpxp_image_field_update_on_user_activation() function calls unlink() on a path built from visitor-supplied signup metadata without realpath() resolution, containment check, or extension allow-list.
- CVE-2026-86596Critical
The s2Member plugin for WordPress in versions up to and including 260927 is vulnerable to Remote Code Execution via the 'item_name' parameter. Insufficient sanitization in strip_php_tags_deep() only strips literal '<?' sequences, and a post-interpolation placeholder cleanup reassembles a valid '<?php' opener after the attacker-controlled value has already been embedded in the email template.
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