CVE-2000-0073 is a buffer overflow vulnerability identified in the Microsoft Rich Text Format (RTF) reader component of Windows 2000, specifically affecting version 4.0. The vulnerability arises when the RTF reader processes a malformed control word within an RTF document. A control word in RTF defines formatting commands, and improper handling of these can lead to memory corruption. In this case, the buffer overflow occurs due to inadequate bounds checking on the control word data, allowing an attacker to overwrite memory buffers. The primary impact of this vulnerability is a denial of service (DoS) condition, where the system or application processing the malicious RTF file can crash or become unresponsive. The vulnerability does not appear to allow for code execution or compromise of confidentiality or integrity, as indicated by the CVSS vector (AV:N/AC:L/Au:N/C:N/I:N/A:P). The attack vector is network-based, requiring no authentication or user interaction beyond opening or processing a crafted RTF file. Microsoft has released a patch addressing this issue, documented in security bulletin MS00-005. No known exploits have been reported in the wild, but the vulnerability remains a concern for systems still running unpatched Windows 2000 environments that process RTF documents, such as email clients or document viewers.

For European organizations, the primary impact of this vulnerability is the potential disruption of services due to denial of service attacks. Organizations relying on legacy Windows 2000 systems, particularly those that automatically process or preview RTF documents (e.g., email gateways, document management systems), could experience system crashes or application failures. This could lead to operational downtime, affecting business continuity and productivity. While the vulnerability does not compromise data confidentiality or integrity, the availability impact could be significant in environments where legacy systems are critical. Additionally, denial of service conditions could be leveraged as part of a broader attack strategy to distract or degrade defenses. Given the age of the affected software, most modern European enterprises are unlikely to be directly impacted; however, sectors with legacy infrastructure—such as certain government agencies, industrial control systems, or specialized legacy applications—may still be at risk.

To mitigate this vulnerability, European organizations should ensure that all Windows 2000 systems are fully patched with the update provided in Microsoft Security Bulletin MS00-005. Given the obsolescence of Windows 2000, organizations should prioritize upgrading to supported operating systems to eliminate exposure. For environments where legacy systems must remain operational, implement network-level controls to restrict access to these systems, such as firewall rules limiting inbound traffic and segmentation to isolate vulnerable hosts. Disable automatic processing or previewing of RTF files in email clients and document viewers where possible to reduce the attack surface. Employ intrusion detection systems (IDS) or intrusion prevention systems (IPS) with signatures that can detect malformed RTF payloads indicative of exploitation attempts. Regularly audit and monitor legacy systems for unusual crashes or service interruptions that may indicate exploitation attempts. Finally, educate users about the risks of opening unsolicited or unexpected RTF documents, especially from untrusted sources.