CVE-2026-67184 in TinyWeb
Summary
by MITRE • 07/28/2026
TinyWeb through 0.0.8 contains a null pointer dereference vulnerability that allows unauthenticated remote attackers to crash worker processes by sending a malformed HTTP request line with an invalid version string. The HttpParser::execute() function fails to allocate the Url object when version parsing fails, leaving the url pointer NULL, and buildResponse() subsequently dereferences this NULL pointer without checking the valid_requ flag, producing a SIGSEGV that terminates the worker process and, when repeated across all workers, takes the server permanently offline until manually restarted.
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Analysis
by VulDB Data Team • 07/28/2026
This vulnerability exists within the TinyWeb HTTP server version 0.0.8 and earlier, representing a critical null pointer dereference flaw that can be exploited by unauthenticated remote attackers to cause service disruption. The issue stems from inadequate input validation within the HTTP request parsing mechanism, specifically in how the HttpParser::execute() function handles malformed version strings in HTTP request lines. When an attacker sends a request containing an invalid version string, the parsing process fails to properly allocate the Url object, resulting in a NULL pointer assignment to the url variable. This failure occurs because the parser does not adequately validate the version string before attempting to construct the URL object, creating a scenario where downstream code operates on uninitialized memory references.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable complete server outages through a cascading failure mechanism. The buildResponse() function subsequently attempts to dereference the NULL url pointer without proper validation checks, specifically failing to examine the valid_requ flag that should indicate whether the request parsing was successful. This fundamental programming error leads to a segmentation fault (SIGSEGV) that terminates individual worker processes. When an attacker repeatedly sends malicious requests, they can systematically crash all available worker processes, effectively taking the entire server offline until manual intervention occurs for restart and recovery operations.
From a cybersecurity perspective, this vulnerability aligns with CWE-476 which identifies null pointer dereference as a common weakness in software security implementations. The attack vector follows patterns consistent with the ATT&CK technique T1499.004 for network denial of service, where adversaries exploit software flaws to disrupt availability. The vulnerability demonstrates poor error handling practices and inadequate defensive programming measures that are frequently observed in embedded systems and lightweight server implementations. The fact that this affects an unauthenticated remote attack vector significantly increases the exposure risk as no credentials or privileged access are required to exploit the flaw.
Mitigation strategies should focus on implementing proper input validation and defensive programming techniques within the HTTP parser implementation. The HttpParser::execute() function must include comprehensive error checking after version string parsing operations, ensuring that URL object allocation failures are properly handled before downstream code execution. Additionally, the buildResponse() function should incorporate null pointer validation checks prior to dereferencing any pointers that may have resulted from failed parsing operations. Implementing proper state management through the valid_requ flag and ensuring its correct evaluation would prevent the segmentation fault condition. System-level protections such as process isolation, automatic restart mechanisms, and resource monitoring can provide additional layers of defense against exploitation attempts while the core software vulnerability is being patched or updated.