Source: cve@mitre.org
Format string vulnerability in the log routine for gopher daemon (gopherd) 3.0.3 allows remote attackers to cause a denial of service and possibly execute arbitrary code.
Gopherd, a legacy information retrieval protocol daemon, is vulnerable to a format string vulnerability that allows remote attackers to cause a denial of service (DoS) and potentially remote code execution (RCE). Exploiting this flaw could lead to complete system compromise. This vulnerability is a significant risk due to the potential for unauthorized access and data exfiltration.
Step 1: Payload Delivery: The attacker crafts a malicious gopher request. This request includes a specially crafted string containing format string specifiers (e.g., %x, %s, %n) within the request parameters, which are then passed to the log function.
Step 2: Request Processing: The gopherd daemon receives and processes the malicious request. The request parameters, including the format string payload, are passed to the log function for logging.
Step 3: Format String Execution: The log function, due to the lack of input validation, passes the attacker-controlled format string to a format string function like printf.
Step 4: Memory Manipulation: The format string specifiers are interpreted by printf, allowing the attacker to read from or write to arbitrary memory locations. This can lead to information disclosure, denial of service, or, in some cases, remote code execution.
Step 5: Exploitation: Depending on the attacker's payload, the exploitation can lead to a crash (DoS) or, if successful, arbitrary code execution, allowing the attacker to gain control of the system.
The vulnerability lies within the log routine of gopherd 3.0.3. The log function, responsible for writing log messages, fails to properly sanitize user-supplied input before passing it to format string functions like printf. This allows an attacker to craft a malicious gopher request containing format string specifiers (e.g., %x, %s, %n) within the request parameters. These specifiers are then interpreted by printf, leading to memory leaks, arbitrary memory writes, and ultimately, control over the program's execution flow. The root cause is the lack of input validation and sanitization of user-controlled data before it is used as a format string argument. Specifically, the code doesn't check the format string specifiers, allowing an attacker to read and write to arbitrary memory locations. This can lead to a buffer overflow or other memory corruption issues.
This vulnerability is not directly associated with specific APT groups or malware campaigns due to its age. However, any attacker could potentially leverage this vulnerability. This vulnerability is not listed in the CISA KEV catalog.
Network traffic analysis: Examine gopher traffic for unusual request parameters containing format string specifiers (e.g., %x, %s, %n).
Log analysis: Monitor gopherd logs for error messages or crashes that may indicate exploitation attempts. Look for unusual patterns in log entries that include format string specifiers.
Intrusion Detection Systems (IDS): Implement IDS rules to detect malicious gopher requests containing format string payloads.
Memory forensics: If a system crash occurs, analyze memory dumps for evidence of format string exploitation, such as corrupted memory regions or unexpected code execution.
Upgrade: Upgrade to a patched version of gopherd or a more secure alternative. Since gopherd is a legacy protocol, consider disabling it if it is not required.
Input Validation: Implement robust input validation to sanitize all user-supplied data before passing it to format string functions. This includes checking for and removing or escaping format string specifiers.
Least Privilege: Run the gopherd daemon with the least privileges necessary to perform its function.
Web Application Firewall (WAF): If applicable, configure a WAF to filter malicious requests containing format string payloads.
Regular Security Audits: Conduct regular security audits and penetration testing to identify and address vulnerabilities.