CVE-2012-4896 in SumatraPDF
Summary
by MITRE
Heap-based buffer overflow in SumatraPDF before 2.1 allows remote attackers to execute arbitrary code via a crafted PDF document, a different vulnerability than CVE-2012-4895.
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Analysis
by VulDB Data Team • 12/14/2021
The vulnerability identified as CVE-2012-4896 represents a critical heap-based buffer overflow flaw in SumatraPDF version 2.0 and earlier, which enables remote code execution through maliciously crafted PDF documents. This vulnerability specifically affects the PDF parsing functionality within the SumatraPDF reader, making it a significant threat to users who frequently handle PDF files from untrusted sources. The flaw resides in how the application processes certain PDF elements, particularly those related to memory allocation and data handling during document rendering. Unlike CVE-2012-4895 which targeted a different aspect of the PDF processing engine, CVE-2012-4896 focuses on heap memory corruption that occurs when the application attempts to store data beyond the allocated buffer boundaries. This type of vulnerability falls under CWE-122, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations.
The technical implementation of this vulnerability involves the exploitation of improper input validation within the PDF parsing routines. When SumatraPDF encounters a specially crafted PDF document containing malformed data structures, the application's memory management routines fail to properly validate buffer sizes, leading to memory corruption that can be leveraged by attackers. The heap-based nature of this vulnerability means that the overflow occurs within dynamically allocated memory regions, making it particularly dangerous as it can overwrite critical program data, function pointers, or return addresses. Attackers can manipulate the PDF content to force the application into allocating insufficient memory for specific data elements, then write beyond these boundaries to overwrite adjacent heap memory. This memory corruption can be carefully orchestrated to redirect program execution flow, ultimately allowing remote attackers to execute arbitrary code with the privileges of the affected user. The vulnerability demonstrates characteristics consistent with ATT&CK technique T1203, which involves the exploitation of memory corruption vulnerabilities for code execution.
The operational impact of CVE-2012-4896 extends beyond simple remote code execution, as it represents a serious threat to user security and system integrity. Organizations that rely on SumatraPDF for document viewing, particularly those handling sensitive or confidential information, face significant risk from this vulnerability. The remote exploitation capability means that attackers can compromise systems without requiring physical access or user interaction beyond opening the malicious document. This vulnerability affects users across various operating systems where SumatraPDF is deployed, making it a widespread concern for enterprise environments. The fact that this vulnerability exists in versions prior to 2.1 highlights the importance of keeping software updated, as the flaw was addressed in subsequent releases through proper bounds checking and memory management improvements. The vulnerability also demonstrates the broader challenge of PDF reader security, where complex document parsing engines become attack surfaces due to the intricate nature of PDF format specifications and the need for comprehensive input validation. Organizations should consider implementing additional security measures such as sandboxing PDF readers and restricting PDF file downloads from untrusted sources to mitigate the risk associated with this vulnerability.