CVE-2026-94018 in ThreadX
Summary
by MITRE • 10/20/2026
The Web add-on's HTTP server dereferences and releases an uninitialized pointer when it detects a `Content-Length` underflow while processing a `PUT` request. The condition is reachable by an unauthenticated remote client with a single malformed request.
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Analysis
by VulDB Data Team • 10/20/2026
This vulnerability represents a critical memory management error within the HTTP server component of a web add-on, specifically triggered during the handling of PUT requests that contain malformed Content-Length headers. The core technical flaw lies in the application's failure to properly initialize pointers before attempting to dereference them when an underflow condition is detected. In standard software development practices, variables and memory addresses must be explicitly initialized to safe default values or null states prior to use. However, in this scenario, the code path responsible for validating the Content-Length header fails to ensure that subsequent pointer operations are performed on valid, allocated memory regions. When a remote client submits a PUT request with a Content-Length value that results in an underflow calculation, the application logic attempts to access or release resources associated with an uninitialized pointer. This leads directly to undefined behavior, which typically manifests as a segmentation fault or general protection violation, causing the server process to crash abruptly.
The operational impact of this vulnerability is severe due to its remote and unauthenticated nature. An attacker does not require any form of authentication or prior interaction with the system to exploit this flaw. By sending a single, carefully crafted HTTP PUT request containing a malformed Content-Length header that triggers the underflow condition, an external adversary can induce a denial-of-service state against the target service. The immediate consequence is the termination of the web add-on's server process, rendering the associated functionality unavailable until the service is manually restarted or automatically recovered by a watchdog mechanism. This lack of resilience means that even if automated restarts are in place, repeated exploitation could lead to resource exhaustion or instability in dependent systems. Furthermore, depending on the specific memory layout and compiler optimizations, such uninitialized pointer dereferences can sometimes be leveraged for more sophisticated attacks beyond simple denial-of-service, potentially leading to arbitrary code execution if an attacker can control the garbage values present in the uninitialized memory space, although the primary reported impact is service disruption.
From a classification perspective, this vulnerability aligns with CWE-457, which describes the use of an uninitialized variable, and more specifically CWE-824 regarding access to uninitialized pointer. The exploitation technique falls under MITRE ATT&CK tactic T1499, Endpoint Denial of Service, as it aims to disrupt the availability of a specific component on the endpoint or server infrastructure. It also relates to T1055, Process Injection, if the underlying memory corruption allows for control flow hijacking, though the primary vector is resource exhaustion through crash induction. The vulnerability highlights a fundamental gap in input validation and error handling routines within the HTTP parsing logic.
To mitigate this risk, developers must implement rigorous defensive programming practices focused on memory safety. First, all pointers involved in request processing should be explicitly initialized to null or valid allocated states before any conditional checks are performed. Second, input validation for Content-Length headers must include robust range checking and type verification to prevent integer underflows from occurring during arithmetic operations. If an underflow is detected, the system should gracefully reject the malformed request with a 400 Bad Request response rather than attempting to proceed with resource deallocation or pointer dereferencing on invalid data. Additionally, implementing heap protection mechanisms such as Address Sanitizer (ASan) during development and testing phases can help identify these uninitialized access patterns early in the software lifecycle. For deployed systems, deploying Web Application Firewalls that inspect HTTP headers for anomalies may provide a layer of defense against malformed requests until a permanent code patch is applied. Regular security audits focusing on memory management errors are essential to prevent similar vulnerabilities from persisting in network-facing components.