Source: cve@mitre.org
Buffer overflow in FreeBSD libmytinfo library allows local users to execute commands via a long TERMCAP environmental variable.
FreeBSD systems are vulnerable to a local privilege escalation attack due to a buffer overflow in the libmytinfo library. By setting a maliciously crafted TERMCAP environment variable, an attacker can overwrite memory and potentially execute arbitrary code, gaining unauthorized access to the system.
Step 1: Environment Variable Setup: The attacker sets the TERMCAP environment variable to a long string. This string contains malicious data designed to overwrite memory.
Step 2: Vulnerable Application Execution: A program that utilizes the libmytinfo library is executed. This could be a terminal emulator, a system utility, or any application that reads terminal capabilities.
Step 3: Library Interaction: The vulnerable application calls functions within libmytinfo that process the TERMCAP variable.
Step 4: Buffer Overflow: The libmytinfo library attempts to copy the attacker-controlled TERMCAP string into a fixed-size buffer without proper bounds checking. The oversized string overflows the buffer, overwriting adjacent memory regions.
Step 5: Code Execution: The attacker's crafted TERMCAP string overwrites critical memory locations, such as function pointers or return addresses. When the application attempts to use these overwritten values, it jumps to the attacker's injected code or a location controlled by the attacker, resulting in arbitrary code execution.
The vulnerability lies within the libmytinfo library, specifically in how it handles the TERMCAP environment variable. The library fails to properly validate the size of the TERMCAP string before copying it into a fixed-size buffer. This results in a buffer overflow when a long TERMCAP value is provided. The overflow overwrites adjacent memory, potentially including critical data like function pointers or control structures. By carefully crafting the TERMCAP string, an attacker can overwrite these memory locations with malicious code or pointers to it, leading to arbitrary code execution with the privileges of the user running the vulnerable application. The root cause is a lack of bounds checking during the TERMCAP parsing and copying process, a classic example of a memory corruption vulnerability.
Due to the age of the vulnerability, specific APT groups are unlikely to be actively targeting this specific vulnerability. However, it's possible that older malware or tools used by various groups could incorporate this exploit. This vulnerability is not listed on the CISA KEV.
Monitor system logs for unusually long TERMCAP environment variables.
Analyze process memory dumps for evidence of buffer overflows in applications that use libmytinfo.
Network traffic analysis may reveal attempts to exploit the vulnerability if the vulnerable application is network-facing, though this is less likely in this local privilege escalation scenario.
Use file integrity monitoring to detect changes to system binaries or libraries related to libmytinfo.
Upgrade to a patched version of FreeBSD that addresses the buffer overflow in libmytinfo. This is the primary and most effective remediation.
Implement input validation to restrict the length of the TERMCAP environment variable. This is a workaround and not a complete fix.
Apply the principle of least privilege. Limit the permissions of users and applications to reduce the impact of a successful exploit.
Use a memory protection mechanism like Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP) to make exploitation more difficult, even if a buffer overflow occurs.
Regularly scan systems for known vulnerabilities using vulnerability scanners.