CVE-2000-0756 in Outlook
Summary
by MITRE
Microsoft Outlook 2000 does not properly process long or malformed fields in vCard (.vcf) files, which allows attackers to cause a denial of service.
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Analysis
by VulDB Data Team • 05/09/2019
The vulnerability identified as CVE-2000-0756 represents a classic buffer overflow condition affecting Microsoft Outlook 2000 when processing vCard files with excessively long or malformed field data. This issue stems from inadequate input validation mechanisms within the email client's vCard parsing functionality, where the application fails to properly sanitize or limit the length of data fields during file processing. The vulnerability specifically targets the vCard format which is used for electronic business cards and contact information exchange, making it particularly dangerous in environments where users frequently receive contact information from external sources.
The technical flaw manifests when Outlook 2000 encounters vCard files containing fields that exceed predetermined memory allocation limits or contain malformed data structures. This improper handling can lead to memory corruption within the application's heap management system, causing unpredictable behavior including application crashes, system instability, and potential denial of service conditions. The vulnerability falls under the CWE-121 category of stack-based buffer overflow, though in this case the overflow occurs within heap memory management during vCard processing operations. The attack vector is straightforward requiring only the delivery of a malicious vCard file to the target system, making it particularly effective for social engineering campaigns or automated exploitation attempts.
From an operational impact perspective, this vulnerability creates significant security concerns for organizations relying on Outlook 2000 for email communications. The denial of service condition can disrupt business operations by rendering email clients unavailable to users, potentially affecting critical communication channels. Attackers can exploit this weakness to repeatedly crash Outlook applications, creating persistent disruptions that may require system restarts or manual intervention to resolve. The vulnerability also demonstrates how seemingly benign file formats can be weaponized for malicious purposes, highlighting the importance of proper input validation in email client applications. Organizations may experience increased help desk requests, reduced productivity, and potential escalation to more serious security incidents if the vulnerability is not properly addressed.
Mitigation strategies for CVE-2000-0756 should focus on immediate application of vendor patches and updates, as Microsoft released security updates specifically addressing this vulnerability. Network administrators should implement email filtering mechanisms to scan and block suspicious vCard attachments before they reach end users, leveraging content inspection tools that can identify malformed or potentially malicious contact information files. Additionally, user education programs should emphasize the importance of not opening unexpected vCard attachments, particularly from unknown senders or when received through untrusted channels. System hardening measures including memory protection features, application whitelisting, and restricted user permissions can further reduce the attack surface. The vulnerability also underscores the necessity of regular security assessments and vulnerability management processes to identify and remediate similar issues in legacy applications that may not receive ongoing security support from vendors.