Buffer overflow in a certain ActiveX control in SkyFexClient.ocx 1.0.2.77 in SkyFex Client 1.0 allows remote attackers to execute arbitrary code via long strings in the first four arguments to the Start method.
SkyFex Client 1.0 contains a critical buffer overflow vulnerability in its ActiveX control, allowing remote attackers to execute arbitrary code on vulnerable systems. Exploitation occurs through crafted input to the Start method, potentially leading to complete system compromise and data exfiltration. This vulnerability poses a significant risk due to its potential for remote code execution and widespread impact on systems running the affected software.
Step 1: Payload Delivery: The attacker crafts a malicious HTML page or other document that instantiates the vulnerable SkyFexClient.ocx ActiveX control.
Step 2: Method Invocation: The attacker's crafted document calls the Start method of the ActiveX control, providing four arguments.
Step 3: Malicious Input: The attacker provides excessively long strings as the first four arguments to the Start method. These strings are designed to overwrite specific memory locations.
Step 4: Buffer Overflow: The Start method attempts to copy the attacker-controlled, oversized strings into a fixed-size buffer within the control's memory.
Step 5: Code Execution: The overflow overwrites critical memory areas, including the return address. When the Start method completes, the overwritten return address directs program execution to the attacker-controlled payload (e.g., shellcode) injected into the buffer or other memory locations.
Step 6: System Compromise: The attacker's shellcode executes, granting the attacker control over the compromised system, allowing for actions such as data theft, malware installation, or system takeover.
The vulnerability lies within the SkyFexClient.ocx ActiveX control, specifically version 1.0.2.77, used by SkyFex Client 1.0. The Start method, which accepts multiple string arguments, fails to properly validate the size of the input strings. This lack of bounds checking allows an attacker to provide excessively long strings as arguments. When these oversized strings are copied into a fixed-size buffer within the control's memory space, a buffer overflow occurs. This overwrites adjacent memory regions, including potentially the return address, allowing the attacker to control the program's execution flow. The root cause is a missing or inadequate input validation mechanism, leading to a classic buffer overflow condition.