CVE-2021-47775: YouTube Downloader Buffer Overflow Flaw

CVE-2021-47775 Overview

CVE-2021-47775 is a buffer overflow vulnerability affecting YouTube Video Grabber (now referred to as YouTube Downloader) version 1.9.9.1. This vulnerability allows attackers to execute arbitrary code by overwriting the Structured Exception Handler (SEH). Attackers can craft a malicious payload of 712 bytes with SEH manipulation to trigger a bind shell connection on a specified local port, potentially leading to complete system compromise.

Critical Impact

This buffer overflow enables arbitrary code execution through SEH overwrite, allowing attackers to establish a bind shell and gain persistent access to the target system.

Affected Products

• YouTube Video Grabber 1.9.9.1
• YouTube Downloader 1.9.9.1 (renamed product)
• LiteXMedia YouTube Grabber 1.9.9.1

Discovery Timeline

• 2026-01-15 - CVE CVE-2021-47775 published to NVD
• 2026-01-16 - Last updated in NVD database

Technical Details for CVE-2021-47775

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption flaw that occurs when the application writes data past the end of an allocated buffer. In the context of YouTube Video Grabber 1.9.9.1, the buffer overflow allows attackers to overwrite critical memory structures, specifically targeting the Structured Exception Handler chain on Windows systems.

The attack requires local access and user interaction, meaning an attacker would need to convince a user to process a maliciously crafted input or file. Once triggered, the overflow enables precise control over program execution flow by corrupting the SEH chain, a mechanism Windows uses to handle runtime exceptions.

Root Cause

The root cause of this vulnerability lies in insufficient bounds checking when processing user-supplied input within YouTube Video Grabber. The application fails to properly validate the length of input data before copying it into a fixed-size buffer, resulting in a classic stack-based buffer overflow condition. This allows an attacker to write beyond the allocated memory space and corrupt adjacent memory structures, including the SEH records stored on the stack.

Attack Vector

The attack vector is local, requiring the attacker to have access to the target system or to social engineer a user into opening a malicious file or input. The exploitation involves crafting a payload of exactly 712 bytes designed to overflow the vulnerable buffer and strategically overwrite the SEH handler address. When an exception is triggered (either naturally or forced by the overflow), the corrupted SEH handler redirects execution to attacker-controlled code, establishing a bind shell that listens for incoming connections on a specified port.

The exploitation mechanism leverages SEH overwrite techniques common in Windows exploitation, where the attacker positions shellcode in memory and uses SEH chain corruption to gain code execution when exception handling is invoked.

Detection Methods for CVE-2021-47775

Indicators of Compromise

• Presence of YouTube Video Grabber or YouTube Downloader version 1.9.9.1 on endpoint systems
• Unexpected bind shell processes or unusual listening ports on workstations
• Process execution anomalies following launch of YouTube Grabber application
• Crash dumps or exception logs indicating SEH chain corruption

Detection Strategies

• Monitor for network connections originating from YouTube Grabber application processes, particularly unexpected listening sockets
• Implement endpoint detection rules for SEH overwrite attack patterns and stack pivot indicators
• Deploy behavioral analysis to detect code execution from exception handlers
• Utilize SentinelOne's behavioral AI to identify memory corruption exploitation attempts

Monitoring Recommendations

• Enable process monitoring for YouTubeGrabber.exe or related executables to detect abnormal behavior
• Configure network monitoring to alert on new listening ports established by media applications
• Review crash reports and Windows Event Logs for application exceptions in YouTube Grabber
• Implement file integrity monitoring on systems where the vulnerable application is installed

How to Mitigate CVE-2021-47775

Immediate Actions Required

• Uninstall YouTube Video Grabber/YouTube Downloader version 1.9.9.1 from all systems immediately
• Audit endpoints for the presence of vulnerable application versions using software inventory tools
• Consider blocking execution of the vulnerable application through application control policies
• Review systems where the application was installed for signs of compromise

Patch Information

At the time of this publication, users should check the LiteXMedia YouTube Grabber vendor website for updated versions that address this vulnerability. Given the severity of this buffer overflow vulnerability, upgrading to the latest available version or removing the application entirely is strongly recommended.

For additional technical details about this vulnerability, refer to Exploit-DB #50471.

Workarounds

• Remove or disable YouTube Video Grabber 1.9.9.1 from all systems until a patched version is available
• Implement application whitelisting to prevent execution of the vulnerable application
• Deploy network segmentation to limit lateral movement if a system is compromised
• Enable Windows exploit protection features such as SEHOP (Structured Exception Handler Overwrite Protection) to mitigate SEH-based attacks

Organizations should prioritize removal of this vulnerable software and implement defense-in-depth strategies including endpoint protection solutions like SentinelOne that can detect and prevent memory corruption exploitation attempts in real-time.