CVE-2000-0847 in C-Client Library
Summary
by MITRE
Buffer overflow in University of Washington c-client library (used by pine and other programs) allows remote attackers to execute arbitrary commands via a long X-Keywords header.
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Analysis
by VulDB Data Team • 04/06/2019
The vulnerability identified as CVE-2000-0847 represents a critical buffer overflow flaw within the University of Washington c-client library, a widely utilized component that forms the foundation for numerous email client applications including the popular Pine email program. This library serves as a critical middleware element for handling internet message access protocol messages and email headers, making it a prime target for exploitation by malicious actors seeking to compromise systems through remote code execution. The flaw specifically manifests when processing the X-Keywords header field in email messages, where the library fails to properly validate input length before copying data into fixed-size buffers, creating an exploitable condition that can be leveraged by remote attackers.
The technical implementation of this vulnerability stems from inadequate bounds checking within the c-client library's header parsing routines, particularly in how it handles the X-Keywords header field. When an email message contains an excessively long X-Keywords header value, the library attempts to copy this data into a predetermined buffer size without proper length validation, resulting in buffer overflow conditions. This overflow can overwrite adjacent memory locations including return addresses and control data structures, allowing attackers to manipulate program execution flow. The vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and can be categorized under CWE-787, representing out-of-bounds write vulnerabilities. From an operational perspective, this flaw enables attackers to execute arbitrary code on systems running affected versions of Pine or other applications that utilize the vulnerable c-client library, potentially leading to complete system compromise and unauthorized access to email communications.
The impact of this vulnerability extends significantly beyond individual system compromise, as it affects a substantial portion of email infrastructure that relied on the University of Washington c-client library. Email clients using this library represent critical communication tools for both individual users and enterprise environments, making the potential attack surface extensive. The remote nature of the exploit means that attackers can trigger the vulnerability without requiring physical access to target systems, and the arbitrary code execution capability provides complete control over compromised systems. Security professionals should note that this vulnerability aligns with ATT&CK technique T1059.007, which involves the use of command and scripting interpreter for execution, and T1068, representing exploit for privilege escalation. The widespread adoption of the c-client library across multiple email applications meant that a single patch could address multiple vulnerable systems, but the vulnerability's existence highlighted the critical importance of proper input validation in networked applications.
Mitigation strategies for CVE-2000-0847 primarily focus on immediate patching of affected systems, with the University of Washington releasing updated versions of the c-client library that include proper bounds checking for header field processing. Organizations should prioritize updating all systems running Pine or other applications utilizing the vulnerable library, as well as implementing network-based protections such as email filtering that can detect and block malformed X-Keywords headers. From a defensive perspective, this vulnerability underscores the necessity of input validation at multiple layers within application architectures and demonstrates the critical importance of maintaining up-to-date security patches for widely used middleware components. The incident also emphasizes the value of secure coding practices, particularly the need for developers to implement proper buffer management and input validation mechanisms to prevent similar vulnerabilities from emerging in future implementations.