Unspecified vulnerability in the Brazilian Portuguese Grammar Checker in Microsoft Office 2003 and the Multilingual Interface for Office 2003, Project 2003, and Visio 2003 allows user-assisted remote attackers to execute arbitrary code via crafted text that is not properly parsed.
Microsoft Office 2003 is vulnerable to a remote code execution (RCE) attack due to a flaw in the Brazilian Portuguese grammar checker. An attacker can craft malicious text that, when processed by the grammar checker, leads to the execution of arbitrary code on the victim's system, potentially allowing for complete system compromise and data exfiltration.
Step 1: Payload Delivery: The attacker crafts a malicious document (e.g., a Word document) containing specially crafted text designed to trigger the vulnerability. This text is specifically formatted to exploit the grammar checker's parsing flaws. Step 2: User Interaction: The victim opens the malicious document in Microsoft Office 2003, or the document is opened by a vulnerable application (e.g., Project 2003, Visio 2003) that uses the grammar checker. Step 3: Grammar Checker Activation: The grammar checker is automatically invoked, or the user manually initiates a grammar check on the document. Step 4: Parsing and Vulnerability Trigger: The grammar checker parses the malicious text. Due to the parsing error, the crafted text causes a memory corruption issue, such as a buffer overflow. Step 5: Code Execution: The memory corruption allows the attacker to overwrite critical memory locations, including the return address, and redirect program execution to attacker-controlled code (the payload). This payload could be shellcode or other malicious instructions. Step 6: System Compromise: The attacker's code executes, granting the attacker control over the victim's system. This could involve installing malware, stealing data, or other malicious activities.
The vulnerability stems from a parsing error within the Brazilian Portuguese grammar checker component of Microsoft Office 2003. The grammar checker, when processing specially crafted text, fails to properly validate or sanitize input, leading to a memory corruption issue. This could manifest as a buffer overflow or other memory-related vulnerability. The root cause is likely a flawed implementation of the parsing logic, potentially involving incorrect handling of string lengths, data types, or memory allocation within the grammar checking routines. The specific function or logic flaw is not explicitly stated in the CVE but is related to how the grammar checker processes text, likely involving a heap overflow or stack overflow due to insufficient bounds checking during parsing of the crafted text. The lack of proper input validation allows the attacker to control program execution by overwriting critical memory regions.