Source: secure@microsoft.com
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) flaw in its Brazilian Portuguese grammar checker. This vulnerability, triggered by maliciously crafted text, allows attackers to execute arbitrary code on a victim's system, potentially leading to complete system compromise and data theft. Successful exploitation requires user interaction, such as opening a specially crafted document.
Step 1: Payload Delivery: The attacker crafts a malicious document (e.g., a Word document) containing specially formatted text designed to exploit the grammar checker. This text is likely written in a way that exploits a parsing vulnerability in the Brazilian Portuguese grammar checker. Step 2: User Interaction: The victim opens the malicious document in Microsoft Office 2003, or potentially interacts with the document in a way that triggers the grammar checker (e.g., running a spell check or grammar check). Step 3: Vulnerability Trigger: The grammar checker processes the crafted text. Due to the parsing error, the crafted text causes a memory corruption event, such as a buffer overflow. Step 4: Code Execution: The memory corruption allows the attacker to overwrite critical memory locations, potentially including the instruction pointer (IP) or other control flow data. This allows the attacker to redirect program execution to a location containing malicious code (the payload). Step 5: Payload Execution: The attacker's malicious code is executed, 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 user-supplied text, fails to properly validate or sanitize input, leading to a memory corruption issue. While the exact nature of the flaw is unspecified in the CVE description, it likely involves an issue such as a buffer overflow, format string vulnerability, or an integer overflow during the parsing of the crafted text. The crafted text likely contains specially formatted data that, when processed by the vulnerable grammar checker, overwrites critical memory regions, allowing an attacker to inject and execute malicious code. The lack of specific details in the CVE suggests the vulnerability was complex or the details were withheld to prevent immediate exploitation.
While no specific APT groups are directly linked to this vulnerability, any group with the capability and interest in targeting older systems could potentially leverage it. The lack of specific details makes it difficult to attribute attacks. This vulnerability is not listed on the CISA KEV.
Monitor network traffic for unusual patterns associated with document opening or grammar checker activity, especially if the document is from an untrusted source.
Analyze file hashes of Office documents for known malicious indicators.
Implement host-based intrusion detection systems (HIDS) to monitor for suspicious process behavior, such as unexpected code execution within Office processes.
Examine system logs for evidence of Office application crashes or errors related to the grammar checker component.
Monitor for the creation of suspicious files or registry entries after opening potentially malicious documents.
Upgrade to a supported version of Microsoft Office. This is the most effective remediation, as newer versions are not vulnerable.
Apply all available security updates for Microsoft Office 2003. While updates may not fully mitigate the vulnerability, they may reduce the attack surface or make exploitation more difficult.
Disable the Brazilian Portuguese grammar checker if not required. This reduces the attack surface.
Implement strict file access controls to limit the ability of users to open untrusted documents.
Educate users about the risks of opening documents from untrusted sources and the importance of not enabling macros or other active content in such documents.
Deploy a robust endpoint detection and response (EDR) solution to detect and respond to malicious activity.