CVE-2020-37036: RM Downloader Buffer Overflow Vulnerability

CVE-2020-37036 Overview

CVE-2020-37036 is a local buffer overflow vulnerability affecting RM Downloader version 2.50.60. The vulnerability exists in the Load parameter handling functionality, allowing attackers to execute arbitrary code by overwriting memory through a crafted malicious payload. This vulnerability leverages an egg hunter technique to bypass memory protections, potentially enabling attackers to execute arbitrary commands on the affected system.

Critical Impact

Successful exploitation allows local attackers to execute arbitrary code with the privileges of the application user, potentially leading to complete system compromise through memory corruption techniques.

Affected Products

• RM Downloader 2.50.60

Discovery Timeline

• 2026-01-30 - CVE CVE-2020-37036 published to NVD
• 2026-02-03 - Last updated in NVD database

Technical Details for CVE-2020-37036

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), commonly known as a classic buffer overflow. The flaw resides in the Load parameter processing within RM Downloader 2.50.60, where insufficient bounds checking allows user-supplied input to overflow stack-allocated buffers. When exploited, attackers can overwrite adjacent memory, including critical control structures such as return addresses and saved frame pointers.

The vulnerability requires local access to the system and user interaction to trigger, making it a targeted attack vector. The attack leverages an egg hunter shellcode technique, which is particularly useful when available buffer space is limited. The egg hunter searches through memory for a predefined marker ("egg") that precedes the main shellcode payload, allowing execution of larger shellcode even when the initial overflow space is constrained.

Root Cause

The root cause of this vulnerability is improper input validation in the Load parameter handler. The application fails to verify the length of user-supplied data before copying it into a fixed-size buffer on the stack. This classic programming error allows attackers to supply input exceeding the buffer's capacity, causing adjacent memory to be overwritten with attacker-controlled data.

Attack Vector

The attack vector is local, requiring the attacker to have access to the target system. Exploitation involves crafting a specially formatted input file or data stream that, when processed by the Load function, triggers the buffer overflow.

The attack methodology involves:

1. Identifying the exact buffer size and offset to the return address
2. Crafting a payload with NOP sleds and egg hunter shellcode
3. Placing the "egg" marker followed by the main payload in memory
4. Triggering the overflow to redirect execution to the egg hunter
5. The egg hunter locates and executes the main shellcode, which can spawn processes like calc.exe or establish reverse shells

Technical details and proof-of-concept code are available through the Exploit-DB #48628 entry and the GitHub PoC Repository.

Detection Methods for CVE-2020-37036

Indicators of Compromise

• Presence of RM Downloader version 2.50.60 installed on the system
• Unusual process spawning from the RM Downloader application (e.g., cmd.exe, calc.exe, or PowerShell)
• Crash dumps or application faults in RM Downloader indicating memory corruption
• Evidence of egg hunter patterns (short looping shellcode sequences) in process memory

Detection Strategies

• Monitor for RM Downloader application crashes or unexpected terminations that may indicate exploitation attempts
• Implement endpoint detection rules to identify shellcode patterns associated with egg hunter techniques
• Deploy application control policies to prevent execution of unauthorized child processes from RM Downloader
• Use memory protection monitoring to detect stack-based buffer overflow exploitation attempts

Monitoring Recommendations

• Enable Windows Event logging for application crashes and faults related to RM Downloader
• Configure SentinelOne agents to alert on behavioral anomalies such as unexpected process creation chains
• Monitor for file system activity involving suspicious input files being loaded into RM Downloader
• Review endpoint telemetry for indicators of code execution techniques following application exploitation

How to Mitigate CVE-2020-37036

Immediate Actions Required

• Remove or disable RM Downloader 2.50.60 from production systems until a patched version is available
• Implement application whitelisting to prevent unauthorized code execution
• Restrict local user permissions to minimize the impact of successful exploitation
• Deploy endpoint protection solutions capable of detecting buffer overflow exploitation techniques

Patch Information

No vendor patch information is currently available for this vulnerability. Organizations should consult the VulnCheck Advisory on Buffer Overflow for the latest remediation guidance. Consider replacing RM Downloader with an alternative application that receives active security maintenance.

Workarounds

• Uninstall RM Downloader 2.50.60 and use alternative download management software
• If removal is not feasible, run the application in a sandboxed environment with restricted permissions
• Enable Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) system-wide to increase exploitation difficulty
• Implement strict input validation at the operating system level using security tools that can intercept file operations

# Windows DEP Configuration Example
# Enable DEP for all programs via elevated command prompt
bcdedit /set {current} nx AlwaysOn

# Verify DEP status
wmic OS Get DataExecutionPrevention_SupportPolicy