CVE-2018-10388 in TFTP Server SP
Summary
by MITRE
Format string vulnerability in the logMess function in TFTP Server SP 1.66 and earlier allows remote attackers to perform a denial of service or execute arbitrary code via format string sequences in a TFTP error packet.
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Analysis
by VulDB Data Team • 03/16/2024
The vulnerability identified as CVE-2018-10388 represents a critical format string flaw within the TFTP Server SP 1.66 and earlier versions, specifically within the logMess function. This issue arises from improper input validation and handling of user-supplied data within the logging mechanism of the TFTP server implementation. The vulnerability manifests when the server processes error packets containing maliciously crafted format string sequences, which are then passed directly to the logging function without proper sanitization or encoding. Such format string vulnerabilities fall under the CWE-134 classification, which specifically addresses the use of untrusted input in format string functions, making them particularly dangerous due to their potential for arbitrary code execution and system compromise.
The technical exploitation of this vulnerability occurs through the manipulation of TFTP error packets that are transmitted during normal TFTP operations. When a remote attacker crafts a malicious error packet containing format specifiers such as %s, %x, or %n, these sequences are interpreted by the vulnerable logMess function, leading to unintended memory access patterns and potential code execution. The attacker can leverage these format string sequences to read arbitrary memory locations, overwrite critical memory regions, or inject malicious code into the server process. This vulnerability operates at the application layer and requires no authentication or privileged access, making it particularly attractive to threat actors seeking to exploit TFTP servers in network environments where such services are commonly deployed.
The operational impact of CVE-2018-10388 extends beyond simple denial of service scenarios to encompass full system compromise capabilities. Remote attackers can leverage this vulnerability to execute arbitrary code with the privileges of the TFTP server process, potentially leading to complete system takeover. The vulnerability affects TFTP servers that are widely deployed in enterprise networks, educational institutions, and industrial environments where TFTP is used for firmware updates, network device configuration, and file transfers. The attack surface is particularly broad since TFTP servers are often exposed to untrusted networks and may be running with elevated privileges, especially in network infrastructure devices where TFTP services are commonly enabled for automated device management and configuration updates.
Organizations should implement immediate mitigations including upgrading to TFTP Server SP 1.67 or later versions that contain the patched logMess function with proper input validation and sanitization. The fix typically involves implementing proper string formatting techniques that prevent format string exploitation by either using fixed format strings or by properly escaping user-supplied input before processing. Network segmentation and access controls should be enforced to limit exposure of TFTP servers to untrusted networks, while monitoring systems should be configured to detect anomalous TFTP error packet patterns. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for command and scripting interpreter and T1489 for network disruption, while the exploitation techniques align with T1211 for exploitation for privilege escalation and T1068 for exploit for privilege escalation. Security teams should also consider implementing intrusion detection systems that can identify and alert on suspicious TFTP error packet content that may indicate exploitation attempts.