Source: cve@mitre.org
Buffer overflow in Linux splitvt command gives root access to local users.
Local privilege escalation is possible on vulnerable Linux systems due to a buffer overflow in the splitvt command. Successful exploitation allows a local user to gain root access, granting complete control over the compromised system and potentially leading to significant data breaches and system compromise.
Step 1: User Interaction: A local, unprivileged user executes the splitvt command with a specially crafted input.
Step 2: Input Processing: The splitvt command receives the malicious input, which is designed to be larger than the allocated buffer.
Step 3: Buffer Overflow: The oversized input overflows the buffer, overwriting adjacent memory locations, including the stack.
Step 4: Return Address Overwrite: The attacker's crafted input overwrites the return address on the stack with the address of shellcode.
Step 5: Shellcode Execution: When the function returns, the program jumps to the attacker-controlled address, executing the shellcode.
Step 6: Privilege Escalation: The shellcode grants the attacker root privileges, effectively escalating their access level.
The vulnerability lies within the splitvt command, specifically in how it handles user-supplied input. The program fails to properly validate the size of input strings before copying them into a fixed-size buffer. This leads to a buffer overflow when a user provides an input string larger than the allocated buffer. By crafting a malicious input, an attacker can overwrite adjacent memory regions, including the return address on the stack. This allows the attacker to redirect program execution to an address of their choosing, typically to a location containing shellcode. The shellcode, when executed, grants the attacker root privileges. The root cause is a lack of bounds checking on input parameters, a common programming error that allows for memory corruption.
While specific APT groups are not definitively linked to this very old vulnerability, its simplicity and ease of exploitation make it a potential tool for any attacker seeking local privilege escalation. This vulnerability is not listed in the CISA KEV as it is considered a legacy vulnerability.
Monitor system logs for suspicious activity related to the splitvt command, such as unusually long command-line arguments or unexpected behavior.
Analyze core dumps or crash reports for splitvt to identify potential buffer overflow events.
Implement file integrity monitoring to detect any unauthorized modifications to the splitvt binary or related configuration files.
Network monitoring for unusual traffic patterns originating from the compromised host after exploitation.
Upgrade or Remove: The most effective remediation is to remove the splitvt package if it is not required. If it is required, upgrade to a patched version of the operating system that includes a fixed splitvt binary.
Input Validation: Implement robust input validation to ensure that all user-supplied input is properly sanitized and does not exceed the allocated buffer size. This is a general principle for all applications.
Least Privilege: Enforce the principle of least privilege. Users should only have the minimum necessary permissions to perform their tasks.
Regular Patching: Maintain a regular patching schedule to address security vulnerabilities promptly.
Use of modern security tools: Employ tools like ASLR (Address Space Layout Randomization) and DEP (Data Execution Prevention) to mitigate the impact of buffer overflows, even if the vulnerability is not fully patched.