CVE-2019-12412 in Libapreq2
Summary
by MITRE • 11/19/2020
A flaw in the libapreq2 v2.07 to v2.13 multipart parser can deference a null pointer leading to a process crash. A remote attacker could send a request causing a process crash which could lead to a denial of service attack.
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Analysis
by VulDB Data Team • 12/08/2020
The vulnerability identified as CVE-2019-12412 resides within the libapreq2 library version 2.07 through 2.13, specifically within its multipart parser component that handles HTTP request parsing for web applications. This flaw represents a classic null pointer dereference issue that occurs when the parser encounters malformed multipart data structures during HTTP request processing. The affected library is commonly used in web server modules such as mod_perl and other applications that require robust HTTP request parsing capabilities for handling file uploads and form data submissions.
The technical implementation of this vulnerability stems from insufficient input validation within the multipart parsing logic where the software fails to properly check for null pointers before dereferencing them during the processing of boundary markers and content headers. When a remote attacker crafts a specially crafted HTTP request containing malformed multipart content, the parser attempts to access memory locations that have not been properly initialized, resulting in an immediate process crash. This behavior manifests as an unhandled exception that terminates the web server process or application instance handling the request, effectively rendering the service unavailable to legitimate users.
From an operational perspective, this vulnerability creates a significant denial of service risk that can be exploited by any remote attacker with knowledge of the target system's web application interface. The attack vector requires minimal complexity as it only necessitates sending a malformed HTTP request to the vulnerable service, making it particularly dangerous in production environments where such attacks can be automated and scaled. The impact extends beyond simple service disruption to potentially affecting business continuity and user experience, especially in applications where file upload functionality is critical to core operations.
The vulnerability aligns with CWE-476 which specifically addresses null pointer dereference conditions in software development, and demonstrates a clear path from the initial input processing to the final crash state. From an attack framework perspective, this vulnerability could be classified under ATT&CK technique T1499.004 which covers network denial of service attacks, and potentially T1595.001 for reconnaissance activities that identify vulnerable systems. Organizations should prioritize immediate patching of affected systems, as the vulnerability exists across multiple versions of the library and affects various web server configurations that utilize the affected components. The recommended mitigation strategy includes upgrading to libapreq2 version 2.14 or later, implementing proper input validation at the application level, and deploying network-based intrusion detection systems to monitor for suspicious multipart request patterns that could indicate exploitation attempts.