CVE-2003-0161 in Sendmail
Summary
by MITRE
The prescan() function in the address parser (parseaddr.c) in Sendmail before 8.12.9 does not properly handle certain conversions from char and int types, which can cause a length check to be disabled when Sendmail misinterprets an input value as a special "NOCHAR" control value, allowing attackers to cause a denial of service and possibly execute arbitrary code via a buffer overflow attack using messages, a different vulnerability than CVE-2002-1337.
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Analysis
by VulDB Data Team • 08/24/2025
The vulnerability identified as CVE-2003-0161 affects Sendmail versions prior to 8.12.9 and resides within the address parser component specifically in the prescan() function located in parseaddr.c. This flaw represents a classic buffer overflow vulnerability that stems from improper type handling during character and integer conversions. The issue manifests when the function encounters certain input values that it misinterprets as special NOCHAR control values, effectively bypassing critical length validation checks that are essential for preventing buffer overflows.
The technical root cause of this vulnerability lies in the type conversion handling within the prescan() function where char and int types are not properly managed during the parsing process. When Sendmail processes email addresses containing specific sequences, the parser incorrectly interprets certain input values as NOCHAR control codes, which are typically used to indicate end-of-string conditions or special parsing markers. This misinterpretation causes the length validation mechanism to be disabled, allowing malicious input to bypass normal buffer size constraints and potentially overflow the allocated memory space.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enabling remote code execution. Attackers can craft specially formatted email messages that exploit this buffer overflow condition, causing Sendmail to crash or potentially execute arbitrary code on the target system. The vulnerability operates through a different attack vector than CVE-2002-1337, indicating a distinct code path that allows for exploitation, though both vulnerabilities target the same underlying parsing functionality. This makes the system particularly susceptible to attacks where malicious actors can leverage this flaw to gain unauthorized access or disrupt email services.
This vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and aligns with ATT&CK technique T1203, which covers exploitation of remote services through buffer overflow attacks. The improper type handling and conversion errors create a condition where the application's memory management becomes compromised, allowing attackers to manipulate program execution flow. The flaw demonstrates poor input validation and insufficient bounds checking, which are fundamental security principles that should be enforced throughout the application's parsing logic.
Mitigation strategies for CVE-2003-0161 require immediate patching of Sendmail installations to version 8.12.9 or later, which contains the necessary fixes to properly handle type conversions in the prescan() function. System administrators should also implement input sanitization measures and consider deploying intrusion detection systems to monitor for suspicious email traffic patterns that might indicate exploitation attempts. Additionally, the principle of least privilege should be enforced by running Sendmail with minimal required permissions and implementing network segmentation to limit potential attack surface. Regular security assessments and code reviews focusing on type handling and memory management practices are essential to prevent similar vulnerabilities from emerging in other components of the email infrastructure.