Source: cve@mitre.org
Format string vulnerability in DayDream BBS allows remote attackers to execute arbitrary code via format string specifiers in a file containing a ~#RA control code.
DayDream BBS is vulnerable to a critical remote code execution (RCE) flaw. Attackers can exploit a format string vulnerability by injecting malicious code through a specially crafted file containing a specific control code, potentially allowing them to gain complete control of the vulnerable system. This vulnerability poses a significant risk due to its potential for unauthorized access and data compromise.
Step 1: Payload Creation: The attacker crafts a malicious file containing the ~#RA control code followed by format string specifiers designed to manipulate the program's memory. This payload includes format string specifiers like %x (to leak memory), %n (to write to memory), and addresses of critical functions or data structures to overwrite.
Step 2: File Upload/Delivery: The attacker uploads the malicious file to the DayDream BBS, or somehow gets the file into a location where it will be processed by the BBS.
Step 3: Triggering the Vulnerability: The attacker triggers the vulnerability by causing the DayDream BBS to process the malicious file. This might involve accessing a specific feature, viewing a particular file, or triggering a scheduled task within the BBS.
Step 4: Memory Manipulation: The format string specifiers within the file are interpreted by the vulnerable DayDream BBS software. This allows the attacker to read and write to arbitrary memory locations.
Step 5: Code Execution: The attacker uses the memory write capabilities to overwrite a function pointer (e.g., a pointer to a system call) with the address of their injected malicious code. When the overwritten function is called, the attacker's code is executed with the privileges of the DayDream BBS process.
The root cause lies in the DayDream BBS software's improper handling of user-supplied input within a file processing context. Specifically, the software fails to sanitize or validate format string specifiers used within a file containing the ~#RA control code. This allows an attacker to inject format string specifiers (e.g., %x, %n, %s) into the file. When the BBS software processes this file, these specifiers are interpreted, leading to arbitrary memory read and write operations. The attacker can leverage this to overwrite critical memory locations, such as function pointers, and redirect program execution to malicious code of their choosing. This is a classic example of a format string vulnerability, resulting in remote code execution.
Due to the age of the vulnerability and the likely lack of security updates, it is unlikely that specific APT groups are actively targeting this specific vulnerability. However, any threat actor with basic skills could exploit this. This vulnerability is not listed on the CISA KEV.
Monitor network traffic for file uploads or transfers containing the ~#RA control code followed by suspicious format string specifiers (e.g., %x, %n, %s).
Analyze BBS server logs for unusual file access patterns or error messages related to file processing.
Inspect file contents for the presence of format string specifiers, especially in files processed by the BBS.
Monitor system processes for unexpected behavior or the execution of suspicious code within the context of the DayDream BBS process.
Use a file integrity monitoring tool to detect changes to critical system files or BBS configuration files.
The primary remediation is to remove or isolate the vulnerable DayDream BBS instance. Due to the age of the software, security updates are unlikely to be available.
If removal is not immediately possible, restrict access to the BBS to only trusted users and networks.
Implement network segmentation to isolate the BBS from other critical systems.
Monitor network traffic for any signs of exploitation attempts.
Consider using a web application firewall (WAF) to filter out malicious requests, although this is less effective against file-based exploits.
Implement a file integrity monitoring solution to detect unauthorized changes to system files.