Microsoft Outlook 2000, 2002, and 2003 allows user-assisted remote attackers to cause a denial of service (memory exhaustion and interrupted mail recovery) via malformed e-mail header information, possibly related to (1) long subject lines or (2) large numbers of recipients in To or CC headers.
Microsoft Outlook 2000, 2002, and 2003 are vulnerable to a denial-of-service (DoS) attack. Attackers can exploit malformed email headers, specifically those with excessively long subject lines or a large number of recipients, to exhaust the victim's memory and disrupt email recovery, rendering the application unusable. This vulnerability requires user interaction, making it a user-assisted attack.
Step 1: Payload Creation: The attacker crafts an email with a malformed header. This could involve a very long subject line or a large number of recipients in the 'To' or 'CC' fields.
Step 2: Payload Delivery: The crafted email is sent to the victim's Outlook inbox.
Step 3: User Interaction: The victim receives the email. The vulnerability is triggered when the user attempts to view, open, or otherwise interact with the malicious email, or when Outlook attempts to automatically process the email (e.g., during indexing or background processing).
Step 4: Memory Exhaustion: Outlook attempts to parse the malformed header, leading to excessive memory allocation.
Step 5: Denial of Service: The system's memory is exhausted, causing Outlook to become unresponsive, crash, or experience significant performance degradation. Mail recovery may also be interrupted.
The vulnerability stems from inadequate input validation and resource management within Outlook's email header parsing routines. Specifically, the software fails to properly handle extremely long subject lines or a large number of recipients in the 'To' and 'CC' headers. This leads to excessive memory allocation during header processing. The lack of bounds checking on the size of the data being processed, combined with the potential for unbounded memory allocation, results in memory exhaustion. When the application attempts to process the malformed headers, it consumes all available memory, leading to a denial-of-service condition where Outlook becomes unresponsive and mail recovery is interrupted. The root cause is likely a buffer overflow or similar memory-related issue triggered by the oversized header data.