CVE-2001-0099 in Bsguest
Summary
by MITRE
bsguest.cgi guestbook script allows remote attackers to execute arbitrary commands via shell metacharacters in the email address.
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Analysis
by VulDB Data Team • 10/08/2025
The vulnerability identified as CVE-2001-0099 affects the bsguest.cgi guestbook script, which represents a classic example of command injection in web applications. This flaw exists within the input validation mechanisms of the script, specifically in how it processes email addresses submitted by users. The vulnerability stems from improper sanitization of user-supplied data, allowing attackers to inject shell metacharacters that get executed within the context of the web server. The bsguest.cgi script, commonly used for guestbook functionality on websites, fails to properly escape or filter special characters that have meaning in shell contexts, creating a dangerous attack surface where malicious input can be interpreted as shell commands rather than simple text data. This type of vulnerability falls under the category of CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, and represents one of the earliest documented cases of command injection in web applications.
The technical exploitation of this vulnerability requires an attacker to craft a malicious email address that contains shell metacharacters such as semicolons, ampersands, or backticks, which are then processed by the script without proper sanitization. When the guestbook script handles the email address, it may pass this input directly to shell execution functions or system calls, enabling arbitrary command execution on the vulnerable system. This occurs because the script likely uses user input in system calls without proper input validation or escaping, creating a direct pathway for attackers to execute system commands with the privileges of the web server process. The vulnerability is particularly dangerous because it allows attackers to gain complete control over the server's command execution capabilities, potentially leading to unauthorized access to sensitive system resources, data exfiltration, or further compromise of the network infrastructure. This aligns with ATT&CK technique T1059, which covers command and scripting interpreter, specifically targeting the execution of malicious commands through compromised web applications.
The operational impact of CVE-2001-0099 extends beyond simple command execution, as it provides attackers with a persistent foothold within the target environment. Once exploited, attackers can use the compromised guestbook script as a launching point for more sophisticated attacks, including privilege escalation, data manipulation, or the installation of backdoors. The vulnerability's persistence is enhanced by the fact that guestbook scripts are often publicly accessible and frequently used, making them attractive targets for exploitation. Organizations running affected versions of bsguest.cgi face significant risk of unauthorized system access, potential data breaches, and loss of system integrity. The vulnerability demonstrates the critical importance of input validation and proper sanitization in web applications, as even seemingly benign data fields like email addresses can become attack vectors when not properly secured. System administrators should immediately implement mitigations including input filtering, proper output encoding, and application-level restrictions to prevent command injection attacks, while also considering the broader security implications of legacy web applications that may contain similar vulnerabilities. The vulnerability serves as a historical example of why secure coding practices and regular security assessments are essential for maintaining web application security.