CVE-2005-1122 in HTTP Daemon
Summary
by MITRE
Format string vulnerability in cgi.c for Monkey daemon (monkeyd) before 0.9.1 allows remote attackers to cause a denial of service and possibly execute arbitrary code via an HTTP GET request containing double-encoded format string specifiers (aka "double expansion error").
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Analysis
by VulDB Data Team • 05/31/2019
The vulnerability identified as CVE-2005-1122 represents a critical format string flaw within the Monkey web server daemon's CGI processing component. This vulnerability specifically affects versions of the Monkey daemon prior to 0.9.1 and demonstrates a classic double expansion error that occurs during HTTP GET request handling. The flaw exists in the cgi.c file where the web server fails to properly sanitize user-supplied input before using it in format string operations, creating a pathway for malicious exploitation through carefully crafted HTTP requests.
The technical execution of this vulnerability relies on the web server's improper handling of double-encoded format string specifiers within HTTP GET parameters. When a remote attacker submits a specially crafted request containing double-encoded format specifiers such as %s or %x, the Monkey daemon processes these inputs without adequate validation or sanitization. The double expansion error occurs because the server first decodes the input and then processes it through a vulnerable printf-like function, allowing the attacker to manipulate the format string parsing behavior. This creates a scenario where the attacker can control the format string arguments passed to functions like printf, sprintf, or similar string formatting routines, potentially leading to stack corruption and arbitrary code execution.
The operational impact of this vulnerability extends beyond simple denial of service to encompass potential complete system compromise. Attackers can leverage this flaw to execute arbitrary code with the privileges of the web server process, typically running as a low-privilege user but potentially escalating further through additional attack vectors. The vulnerability's ability to cause denial of service means that legitimate users cannot access web services, while the code execution capability allows for full system compromise, data exfiltration, and persistence mechanisms. This makes it particularly dangerous in production environments where the web server handles sensitive information and user requests.
This vulnerability maps directly to CWE-134, which specifically addresses the use of format strings without proper validation, and aligns with ATT&CK techniques related to command and control through web application exploitation. The weakness demonstrates poor input validation practices and inadequate sanitization of user-supplied data before processing. Organizations should implement immediate mitigations including updating to Monkey daemon version 0.9.1 or later, which contains proper format string validation and sanitization. Additional defensive measures include implementing web application firewalls, deploying input validation rules, and monitoring for suspicious HTTP GET requests containing format string specifiers. The vulnerability also highlights the importance of proper error handling and secure coding practices in web server components, particularly those handling user input through CGI interfaces.