Source: cve@mitre.org
Buffer overflow in rcp for AIX 4.3.3, 5.1 and 5.2 allows local users to gain privileges.
A critical buffer overflow vulnerability exists in the rcp utility on IBM AIX systems, allowing local attackers to escalate privileges. Successful exploitation grants unauthorized access, potentially leading to complete system compromise and data exfiltration. This vulnerability, though old, remains a threat on unpatched systems and should be prioritized for remediation.
Step 1: Input Injection: The attacker crafts a malicious filename or path exceeding the allocated buffer size within the rcp utility. This input is typically provided through a local command line invocation of rcp.
Step 2: Buffer Overflow: The rcp utility, when processing the malicious filename/path, copies the oversized input into a fixed-size buffer without proper bounds checking. This overwrites adjacent memory locations.
Step 3: Control Hijack: The overflow overwrites the return address on the stack. The attacker carefully crafts the malicious input to overwrite the return address with the address of injected shellcode, or a location in memory that will lead to code execution.
Step 4: Code Execution: When the rcp function returns, the CPU jumps to the attacker-controlled address. The attacker's shellcode is executed with the privileges of the rcp process, which is often root, granting the attacker elevated privileges.
The vulnerability lies within the rcp (remote copy) utility's handling of user-supplied input. Specifically, the flaw stems from a buffer overflow in how rcp processes the filename or path provided by the user. The program fails to properly validate the size of the input before copying it into a fixed-size buffer. By providing an excessively long filename or path, an attacker can overwrite adjacent memory regions, including critical program data like the return address. This allows the attacker to overwrite the return address with the address of malicious code (shellcode), leading to arbitrary code execution with the privileges of the rcp process, typically root.
While no specific APTs are definitively linked to the exploitation of this specific CVE, the nature of the vulnerability makes it attractive to any attacker seeking privilege escalation. The vulnerability's age and the availability of PoCs mean that it could be used by a wide range of actors. This vulnerability is not listed on the CISA KEV at this time, but should be considered a high-risk vulnerability.
Monitor system logs for unusually long filenames or paths passed to the rcp command.
Analyze process memory dumps for evidence of stack corruption or shellcode injection related to rcp.
Network traffic analysis: While this is a local vulnerability, unusual network activity originating from the compromised host after exploitation should be investigated.
File integrity monitoring to detect changes to system binaries or critical configuration files that may indicate compromise.
Apply the security patches provided by IBM for the affected AIX versions.
Implement least privilege principles, restricting user access to rcp where possible.
Regularly scan systems for vulnerabilities using vulnerability scanners.
Implement a robust intrusion detection and prevention system (IDS/IPS) to monitor for suspicious activity.
Harden the system by disabling unnecessary services and features.