CVE-2021-47881: dataSIMS Avionics Buffer Overflow Flaw

CVE-2021-47881 Overview

CVE-2021-47881 is a local buffer overflow vulnerability affecting dataSIMS Avionics ARINC 664-1 version 4.5.3. This vulnerability allows attackers to overwrite memory by manipulating the milstd1553result.txt file. Attackers can craft a malicious file with carefully constructed payload and alignment sections to potentially execute arbitrary code on Windows systems.

Critical Impact

Local attackers can leverage this buffer overflow to corrupt memory and potentially achieve arbitrary code execution through maliciously crafted input files, affecting system integrity and availability.

Affected Products

• dataSIMS Avionics ARINC 664-1 version 4.5.3
• DDC BU-69414 Software Components
• Windows systems running affected dataSIMS software

Discovery Timeline

• 2026-01-23 - CVE CVE-2021-47881 published to NVD
• 2026-01-26 - Last updated in NVD database

Technical Details for CVE-2021-47881

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow). The dataSIMS Avionics software fails to properly validate the size of data read from the milstd1553result.txt file before copying it into a fixed-size buffer on the stack. When the application processes this file, it does not perform adequate bounds checking, allowing data to overflow past the allocated buffer boundaries.

The local attack vector requires an attacker to have the ability to modify or replace the milstd1553result.txt file on the target system. While user interaction is required to trigger the vulnerability (the application must process the malicious file), no special privileges are needed to craft the malicious input. The primary impact is on system availability, with potential for memory corruption that could lead to application crashes or, in sophisticated attacks, arbitrary code execution.

Root Cause

The root cause of this vulnerability lies in insufficient input validation when parsing the milstd1553result.txt file. The application uses unsafe memory copy operations that do not verify the input data length against the destination buffer size. This classic stack-based buffer overflow pattern occurs when data from an untrusted source (the text file) is copied into a stack-allocated buffer without proper length checks, allowing an attacker to write beyond the buffer boundary and potentially overwrite critical stack data including return addresses.

Attack Vector

The attack requires local access to the system running the vulnerable dataSIMS Avionics software. An attacker must craft a malicious milstd1553result.txt file containing specially constructed payload data with precise alignment to exploit the buffer overflow. When the application reads and processes this file, the oversized input overwrites adjacent memory on the stack.

The attacker must carefully structure the malicious file to include padding for proper alignment and a payload that either corrupts critical data structures or overwrites the return address to redirect execution flow. A public exploit is documented in Exploit-DB #49577, which demonstrates the exploitation technique for this vulnerability.

Detection Methods for CVE-2021-47881

Indicators of Compromise

• Unusually large or malformed milstd1553result.txt files in the dataSIMS working directory
• Application crashes or unexpected behavior when processing MIL-STD-1553 result files
• Presence of files containing NOP sleds, shellcode patterns, or suspicious binary data in text files
• Unexpected modifications to the milstd1553result.txt file timestamps

Detection Strategies

• Monitor file integrity for milstd1553result.txt and related configuration files using file integrity monitoring (FIM) solutions
• Implement application crash monitoring to detect potential exploitation attempts that cause buffer overflow exceptions
• Deploy endpoint detection and response (EDR) solutions capable of identifying buffer overflow exploitation patterns
• Review file access logs for unauthorized modifications to dataSIMS data files

Monitoring Recommendations

• Enable Windows Event logging for application crashes and exceptions related to dataSIMS processes
• Configure SentinelOne to monitor for suspicious memory access patterns and stack corruption indicators
• Implement alerts for file modifications in dataSIMS installation and data directories
• Monitor process behavior for unexpected child process spawning or network connections following file operations

How to Mitigate CVE-2021-47881

Immediate Actions Required

• Restrict file system permissions on the milstd1553result.txt file and its containing directory to prevent unauthorized modifications
• Implement file integrity monitoring on critical dataSIMS data files
• Limit local access to systems running the vulnerable software to authorized personnel only
• Consider network isolation for systems running avionics simulation software

Patch Information

Users should consult the DDC Web Homepage and the DDC Software for BU-69414 page for updated software versions that address this vulnerability. Additional technical details are available in the VulnCheck Advisory - DataSim ARINC.

Workarounds

• Implement strict access controls on the directories containing milstd1553result.txt to prevent unauthorized file modifications
• Deploy application whitelisting to prevent execution of unauthorized code
• Run the dataSIMS application in a sandboxed environment with limited system access
• Validate input files against known-good checksums before processing where operationally feasible

# Configuration example - Restrict file permissions on Windows
# Run in elevated PowerShell

# Set restrictive ACL on the milstd1553result.txt file
$filePath = "C:\Program Files\dataSIMS\milstd1553result.txt"
$acl = Get-Acl $filePath
$acl.SetAccessRuleProtection($true, $false)
$adminRule = New-Object System.Security.AccessControl.FileSystemAccessRule("Administrators","FullControl","Allow")
$acl.AddAccessRule($adminRule)
Set-Acl $filePath $acl