CVE-2002-2396 in Advanced TFTP
Summary
by MITRE
Buffer overflow in Advanced TFTP (atftp) 0.5 and 0.6, if installed setuid or setgid, may allow local users to execute arbitrary code via a long argument to the -g option.
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Analysis
by VulDB Data Team • 04/20/2019
The vulnerability identified as CVE-2002-2396 represents a critical buffer overflow flaw in the Advanced TFTP daemon version 0.5 and 0.6 implementations. This vulnerability specifically affects systems where the atftp binary is installed with setuid or setgid permissions, creating a dangerous privilege escalation vector. The flaw manifests when the daemon processes a long argument provided to the -g option, which is typically used for specifying the file to be retrieved from a remote TFTP server. The buffer overflow occurs in the argument parsing mechanism, where insufficient bounds checking allows an attacker to overwrite adjacent memory locations in the process heap.
The technical nature of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. When the atftp daemon receives an excessively long argument string through the -g option, the program fails to properly validate input length before copying it into a fixed-size buffer. This allows an attacker to overwrite return addresses, function pointers, or other critical memory structures within the executing process. The setuid/setgid permissions amplify the severity because the vulnerable daemon typically runs with elevated privileges, potentially allowing local users to execute arbitrary code with the privileges of the daemon process, which often runs as root or a privileged user.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with a reliable method for privilege escalation within affected systems. Local users who can execute the atftp client with setuid permissions can leverage this flaw to gain unauthorized access to system resources, potentially leading to complete system compromise. The vulnerability affects systems where the atftp daemon is deployed with elevated permissions, which was common in network administration environments where automated file transfers were required. Attackers can craft malicious arguments that overwrite the instruction pointer or other critical control structures, enabling them to inject and execute malicious code within the privileged context of the daemon process.
Mitigation strategies for this vulnerability should focus on immediate patching of affected versions, as the original atftp 0.5 and 0.6 releases contained this flaw. System administrators should ensure that the atftp daemon is not installed with setuid or setgid permissions, as this removes the privilege escalation capability that makes the vulnerability so dangerous. Additionally, implementing input validation and bounds checking mechanisms within the daemon's argument parsing code would prevent the buffer overflow from occurring. Network segmentation and access controls should limit which users can execute the atftp client, while regular security audits should verify that no setuid/setgid binaries exist with known vulnerabilities. The ATT&CK framework categorizes this as a privilege escalation technique under T1068, which involves exploiting weaknesses in system permissions and access controls to gain elevated privileges. Organizations should also consider implementing process monitoring and anomaly detection to identify potential exploitation attempts targeting this type of buffer overflow vulnerability.