CVE-2019-16127
📋 TL;DR
CVE-2019-16127 is an integer overflow vulnerability in Atmel Advanced Software Framework (ASF) 4's flash_read, flash_write, and flash_append functions. This allows attackers to execute arbitrary code or cause denial of service on embedded systems using affected ASF versions. Affected systems include embedded devices and IoT products built with Microchip/Atmel microcontrollers using ASF4.
💻 Affected Systems
- Atmel Advanced Software Framework (ASF)
- Embedded systems using ASF4 with affected flash functions
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete device compromise, data corruption, or permanent bricking of embedded systems.
Likely Case
Denial of service through system crashes or reboots, potentially with data corruption in flash memory.
If Mitigated
Limited impact if input validation is implemented externally or if affected functions aren't exposed to untrusted input.
🎯 Exploit Status
Exploitation requires ability to call affected functions with crafted input. Public proof-of-concept demonstrates the overflow but requires specific access to flash functions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: ASF versions after the vulnerability disclosure (check Microchip for specific patched versions)
Vendor Advisory: https://www.microchip.com/mplab/avr-support/advanced-software-framework
Restart Required: Yes
Instructions:
1. Update ASF to latest version from Microchip website. 2. Recompile and redeploy firmware to affected embedded devices. 3. Test functionality after update.
🔧 Temporary Workarounds
Input validation wrapper
allImplement bounds checking before calling flash_read, flash_write, or flash_append functions
// C code example: validate size parameters before flash operations
if (size > MAX_SAFE_SIZE || offset > MAX_FLASH_SIZE - size) return ERROR;
Function restriction
allRestrict access to vulnerable flash functions to trusted code only
// Implement access control or remove vulnerable functions from exposed APIs
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable embedded devices
- Add external input validation and sanitization for all inputs to flash functions
🔍 How to Verify
Check if Vulnerable:
Check ASF version in project configuration files or build system. Look for use of flash_read, flash_write, or flash_append functions in source code.Check Version:
Check ASF_VERSION in asf.h or project configuration filesVerify Fix Applied:
Verify ASF version is updated and test flash operations with boundary values to ensure no overflow occurs.📡 Detection & Monitoring
Log Indicators:
- Unexpected device reboots
- Flash memory access errors
- Memory corruption warnings
Network Indicators:
- Unusual traffic to embedded device management interfaces
SIEM Query:
Device logs showing repeated crashes or flash access failures from same source🔗 References
- https://census-labs.com/news/2020/10/21/microchip-asf4-integer-overflows-in-flash_read-flash_write-and-flash_append/
- https://www.microchip.com/mplab/avr-support/advanced-software-framework
- https://www.openwall.com/lists/oss-security/2020/10/22/1
- https://census-labs.com/news/2020/10/21/microchip-asf4-integer-overflows-in-flash_read-flash_write-and-flash_append/
- https://www.microchip.com/mplab/avr-support/advanced-software-framework
- https://www.openwall.com/lists/oss-security/2020/10/22/1
