Source: cve@mitre.org
Buffer overflow in Linux Slackware crond program allows local users to gain root access.
Critical vulnerability discovered in the Slackware crond program allows for local privilege escalation to root. Successful exploitation grants attackers complete control over the compromised system, posing a significant risk to data confidentiality, integrity, and availability. This vulnerability, while old, could still be present in legacy systems and requires immediate attention.
Step 1: Identify Target: The attacker identifies a vulnerable Slackware system running crond.
Step 2: Craft Malicious Input: The attacker crafts a specially designed input, likely a job definition or command argument, that exceeds the allocated buffer size within crond.
Step 3: Trigger the Overflow: The attacker submits the malicious input to crond, typically through a local interface or by creating a malicious cron job.
Step 4: Overwrite Memory: The crafted input overflows the buffer, overwriting adjacent memory locations, including the return address on the stack.
Step 5: Execute Shellcode: The attacker's input includes shellcode, which is injected into the overwritten memory. When crond attempts to return from the function, it jumps to the attacker's shellcode.
Step 6: Gain Root Privileges: The shellcode executes with root privileges, granting the attacker complete control over the system.
The vulnerability lies within the crond program's handling of input, likely related to how it processes job definitions or command arguments. The root cause is a buffer overflow, where the program fails to properly validate the size of input data before writing it to a fixed-size buffer. This allows an attacker to overwrite adjacent memory regions, potentially including critical program data like the return address on the stack. By carefully crafting the malicious input, the attacker can overwrite the return address with the address of a shellcode, effectively hijacking program execution and gaining root privileges. The age of the vulnerability suggests a lack of modern security mitigations like ASLR or stack canaries, making exploitation easier.
Due to the age of the vulnerability, it's unlikely to be directly associated with specific, modern APT groups. However, any attacker seeking to gain root access on a Linux system could leverage this exploit. The vulnerability's potential for widespread impact on unpatched systems makes it attractive to various threat actors. CISA KEV status: Not Listed
Monitor system logs (e.g., /var/log/syslog, /var/log/cron) for suspicious cron job entries, especially those with unusual commands or arguments.
Analyze cron job definitions for excessively long or malformed commands.
Examine process memory dumps of crond for signs of buffer overflows or injected shellcode.
Use intrusion detection systems (IDS) with signatures specifically designed to detect buffer overflow attempts against crond or similar cron implementations.
Monitor network traffic for unusual activity originating from the compromised system after a potential exploit, such as attempts to connect to external command and control (C2) servers.
Patch Immediately: Apply the latest security patches for Slackware, ensuring that crond is updated to a version that addresses the buffer overflow vulnerability. This is the most crucial step.
Least Privilege: Ensure that users have the minimum necessary privileges. Avoid granting unnecessary root access.
Input Validation: Implement robust input validation to prevent buffer overflows. This includes limiting the size of input data and sanitizing user-supplied data.
Regular Security Audits: Conduct regular security audits and penetration tests to identify and address vulnerabilities.
Harden the System: Enable security features like ASLR (Address Space Layout Randomization) and stack canaries, if available, to mitigate the impact of buffer overflows.
Monitor System Activity: Implement robust monitoring and logging to detect suspicious activity, including unauthorized access attempts and privilege escalation.