CVE-2016-8386 in Argus
Summary
by MITRE
An exploitable heap-based buffer overflow exists in Iceni Argus. When it attempts to convert a PDF containing a malformed font to XML, the tool will attempt to use a size out of the font to search through a linked list of buffers to return. Due to a signedness issue, a buffer smaller than the requested size will be returned. Later when the tool tries to populate this buffer, the overflow will occur which can lead to code execution under the context of the user running the tool.
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Analysis
by VulDB Data Team • 09/02/2020
The vulnerability described in CVE-2016-8386 represents a critical heap-based buffer overflow within Iceni Argus, a tool designed for PDF to XML conversion. This flaw arises during the processing of malformed font data within PDF documents, specifically when the application attempts to handle font size parameters that exceed the actual buffer capacity. The vulnerability stems from a fundamental signedness issue in the memory allocation and buffer management logic, where the tool incorrectly interprets unsigned size parameters as signed values during the font processing routine.
The technical exploitation of this vulnerability occurs through a cascading sequence of memory management failures that begin with the incorrect handling of font size parameters. When Iceni Argus encounters a malformed font structure, it attempts to allocate memory based on a size parameter that has been incorrectly processed due to the signedness error. This misinterpretation results in the allocation of a buffer that is significantly smaller than the requested size, yet the application proceeds to populate this undersized buffer with data that exceeds its capacity. The heap-based nature of the overflow means that memory corruption occurs in the heap memory space rather than on the stack, making the exploitation more complex but potentially more reliable.
The operational impact of this vulnerability extends beyond simple memory corruption to encompass full code execution capabilities under the privileges of the user running the application. This represents a severe privilege escalation scenario where an attacker could potentially execute arbitrary code with the same permissions as the Iceni Argus process, which typically runs with user-level privileges. The vulnerability's exploitation potential aligns with attack patterns documented in the MITRE ATT&CK framework under the technique of code injection, specifically targeting heap-based buffer overflow conditions that can be leveraged for remote code execution. The flaw demonstrates characteristics consistent with CWE-121, heap-based buffer overflow, and CWE-125, out-of-bounds read, both of which are classified as high-severity vulnerabilities in the Common Weakness Enumeration catalog.
Mitigation strategies for this vulnerability should focus on implementing proper input validation and size parameter handling within the font processing routines of Iceni Argus. The primary fix involves correcting the signedness issue by ensuring that size parameters are properly validated and that buffer allocation logic correctly accounts for the actual size requirements of font data structures. Additionally, implementing bounds checking mechanisms and address space layout randomization would significantly reduce the exploitability of this vulnerability. Organizations should also consider deploying application whitelisting controls and restricting the execution of Iceni Argus with elevated privileges to minimize the potential impact of successful exploitation attempts. The vulnerability highlights the importance of proper memory management practices and the need for comprehensive testing of edge cases in font processing functionality to prevent similar issues in other PDF manipulation tools.