CVE-2017-9544 in Easy Chat Server
Summary
by MITRE
There is a remote stack-based buffer overflow (SEH) in register.ghp in EFS Software Easy Chat Server versions 2.0 to 3.1. By sending an overly long username string to registresult.htm for registering the user, an attacker may be able to execute arbitrary code.
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Analysis
by VulDB Data Team • 11/25/2019
The vulnerability identified as CVE-2017-9544 represents a critical stack-based buffer overflow affecting EFS Software Easy Chat Server versions 2.0 through 3.1. This flaw specifically manifests within the register.ghp component of the application's registration functionality, where the system fails to properly validate input length when processing username strings submitted through the registresult.htm page. The vulnerability exploits the structured exception handling mechanism by overwriting the structured exception handler table entry, creating a potential execution path for malicious code injection. This type of vulnerability falls under CWE-121, which specifically addresses stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations including the stack's exception handling structures.
The technical implementation of this vulnerability occurs when an attacker submits a username string that exceeds the allocated buffer size within the register.ghp module, causing the stack to overflow and potentially overwrite the saved base pointer and return address of the calling function. This memory corruption allows an attacker to manipulate the program's execution flow and inject malicious code that can execute with the privileges of the affected service. The vulnerability is particularly concerning because it operates in a remote context, meaning attackers can exploit it without requiring local access to the system. The attack vector specifically targets the registration process, making it accessible to anyone with network access to the Easy Chat Server instance. This aligns with ATT&CK technique T1203, which describes the use of input validation flaws to execute arbitrary code through remote exploitation.
The operational impact of this vulnerability extends beyond simple code execution, as it could potentially allow attackers to gain unauthorized access to the server's resources and escalate privileges within the network environment. Successful exploitation could result in complete system compromise, data theft, or the establishment of persistent backdoors. The vulnerability affects organizations using EFS Software Easy Chat Server in production environments, particularly those without proper network segmentation or intrusion detection measures. The remote nature of the attack means that organizations may be vulnerable even if they have firewalls in place, as the registration endpoint often remains accessible to external network traffic. Organizations should consider the broader implications of this vulnerability within their threat landscape, as it could serve as an initial access vector for more extensive attacks. The exploitability of this vulnerability is enhanced by the fact that it does not require authentication to the system, making it particularly dangerous for publicly accessible chat servers or those with weak access controls. System administrators should immediately evaluate their deployment of this software and consider implementing network-level mitigations while planning for a definitive patch upgrade. The vulnerability demonstrates the critical importance of input validation and proper buffer management in web applications, particularly those handling user-provided data through registration and authentication mechanisms.