CVE-2000-0583 in vpopmail vchkpw
Summary
by MITRE
vchkpw program in vpopmail before version 4.8 does not properly cleanse an untrusted format string used in a call to syslog, which allows remote attackers to cause a denial of service via a USER or PASS command that contains arbitrary formatting directives.
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Analysis
by VulDB Data Team • 05/05/2019
The vulnerability identified as CVE-2000-0583 affects the vchkpw program within vpopmail versions prior to 4.8, representing a critical security flaw that stems from improper handling of user-supplied input in format string operations. This issue manifests when the program processes USER or PASS commands containing arbitrary formatting directives, creating a scenario where untrusted input directly influences the syslog function call without proper sanitization. The vulnerability resides in the program's failure to implement adequate input validation and sanitization mechanisms, allowing malicious actors to exploit the format string vulnerability through carefully crafted command sequences.
The technical exploitation of this vulnerability occurs through the manipulation of format specifiers within the USER or PASS commands sent to the vpopmail service. When the vchkpw program processes these commands, it passes user-provided data directly to the syslog function without proper cleansing or validation, enabling attackers to inject format string directives that can cause the program to behave unpredictably. This flaw specifically aligns with CWE-134, which describes the weakness of using untrusted data in format string operations, a well-documented vulnerability pattern that has been consistently exploited across various network services and applications. The attack vector operates at the application layer, targeting the mail server authentication mechanism where the vulnerable vchkpw component handles user authentication requests.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can potentially enable more sophisticated attacks depending on the system configuration and the attacker's objectives. While the primary effect described is denial of service, the improper handling of format strings in this context creates opportunities for information disclosure, arbitrary code execution, or system instability. The vulnerability affects the availability of the mail service by causing the vchkpw process to crash or behave erratically when processing maliciously formatted commands, effectively preventing legitimate users from authenticating and accessing their email accounts. This disruption directly impacts business continuity and user productivity, particularly in environments where email services are critical infrastructure components.
Mitigation strategies for CVE-2000-0583 primarily focus on immediate software updates and configuration hardening measures. Organizations should immediately upgrade to vpopmail version 4.8 or later, which contains the necessary patches to address the format string vulnerability in the vchkpw program. Additionally, implementing input validation controls at the network level through firewalls and intrusion detection systems can help filter out malicious commands before they reach the vulnerable service. The implementation of proper access controls and authentication mechanisms, such as those recommended in the ATT&CK framework for credential access and privilege escalation, can further reduce the attack surface. System administrators should also consider implementing monitoring and logging controls to detect anomalous authentication patterns that might indicate exploitation attempts, while maintaining regular security assessments to identify and remediate similar vulnerabilities in other components of the email infrastructure.