CVE-2009-4490 in Mini HTTPd
Summary
by MITRE
mini_httpd 1.19 writes data to a log file without sanitizing non-printable characters, which might allow remote attackers to modify a window s title, or possibly execute arbitrary commands or overwrite files, via an HTTP request containing an escape sequence for a terminal emulator.
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Analysis
by VulDB Data Team • 01/10/2025
The vulnerability identified as CVE-2009-4490 affects mini_httpd version 1.19, a lightweight HTTP server implementation commonly used in embedded systems and network appliances. This issue represents a classic case of insufficient input sanitization that can lead to serious security implications. The flaw specifically manifests when the web server processes HTTP requests and logs them to a file without properly sanitizing non-printable characters that may be embedded within the request data. The vulnerability stems from the server's failure to properly handle terminal escape sequences and control characters that could be present in user-supplied data.
The technical mechanism behind this vulnerability involves the logging subsystem of mini_httpd not properly filtering or escaping special characters that have meaning in terminal emulators and command-line interfaces. When an HTTP request containing non-printable characters or escape sequences is processed, these characters are written directly to the log file without sanitization. This creates a potential attack vector where malicious actors can craft HTTP requests that include terminal control sequences such as ANSI escape codes. These sequences, when interpreted by terminal emulators or text viewers used to examine log files, can manipulate window titles, execute arbitrary commands, or potentially overwrite files through cleverly crafted escape sequences that exploit terminal interpretation behaviors.
The operational impact of this vulnerability extends beyond simple log file corruption, representing a potential privilege escalation vector and information disclosure risk. Attackers who can influence log content can manipulate terminal sessions that display log files, potentially causing unauthorized command execution when administrators view logs in terminal emulators. The vulnerability also presents a risk of file overwrite attacks when log files are processed by applications that do not properly validate the content, allowing attackers to inject malicious sequences that could modify system files or configuration data. This type of vulnerability aligns with CWE-117, which addresses improper output neutralization for logs, and demonstrates how seemingly benign logging functionality can become a security risk when input validation is inadequate.
Mitigation strategies for this vulnerability should focus on implementing proper input sanitization and output escaping mechanisms within the logging subsystem. The most effective approach involves filtering or escaping non-printable characters before writing data to log files, ensuring that terminal control sequences and escape codes are properly neutralized. System administrators should consider implementing log file access controls to limit who can view or modify log content, and should regularly audit log files for suspicious content. Additionally, the server should be updated to newer versions of mini_httpd that have addressed this vulnerability through proper input validation. Organizations should also consider implementing security monitoring solutions that can detect and alert on unusual patterns in log file content that might indicate exploitation attempts. This vulnerability exemplifies the importance of secure logging practices and the potential for terminal escape sequences to create unexpected security implications in web server implementations, aligning with ATT&CK technique T1070.002 for indicator removal and T1059.007 for command and scripting interpreter for command execution through terminal manipulation.