CVE-2022-22819: NXP LPC55S Firmware Buffer Overflow Flaw

CVE-2022-22819 Overview

CVE-2022-22819 is a buffer overflow vulnerability affecting NXP LPC55S66 and LPC55S69 series microcontrollers running ROM version 1B. The vulnerability exists in the parsing mechanism for SB2 (Secure Binary 2) firmware updates, where a buffer overflow occurs before the cryptographic signature is verified. This flaw allows an attacker to achieve non-persistent code execution by crafting a malicious unsigned update package.

Critical Impact

Attackers can bypass secure boot protections and execute arbitrary code on affected microcontrollers through crafted unsigned firmware updates, potentially compromising embedded systems, IoT devices, and industrial control equipment using these processors.

Affected Products

• NXP LPC55S66JBD64 Microcontroller and Firmware
• NXP LPC55S66JBD100 Microcontroller and Firmware
• NXP LPC55S66JEV98 Microcontroller and Firmware
• NXP LPC55S69JBD64 Microcontroller and Firmware
• NXP LPC55S69JBD100 Microcontroller and Firmware
• NXP LPC55S69JEV98 Microcontroller and Firmware

Discovery Timeline

• 2022-03-23 - CVE-2022-22819 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-22819

Vulnerability Analysis

This vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), a classic buffer overflow condition. The flaw resides in the ROM bootloader code of the affected NXP microcontrollers, specifically in the routines responsible for parsing SB2 format firmware update files.

The critical security failure is that the buffer overflow occurs during the initial parsing phase—before any signature verification takes place. This design flaw fundamentally undermines the secure boot chain, as an attacker can trigger memory corruption with completely unsigned and unauthenticated data. The vulnerability requires local access and user interaction (such as initiating a firmware update), but no privileges are required on the target system.

Successful exploitation results in non-persistent code execution, meaning the malicious code runs in the context of the bootloader but does not persist across device resets. However, this is sufficient for attackers to extract secrets, modify runtime behavior, or potentially escalate to persistent compromise depending on the device's security architecture.

Root Cause

The root cause is insufficient bounds checking in the SB2 update parser within the ROM code. When processing the SB2 file structure, the parser accepts size values from the update file without proper validation, allowing an attacker-controlled size to cause buffer overflow conditions. Since ROM code cannot be patched after manufacturing, devices with ROM version 1B remain vulnerable unless additional software mitigations are implemented at higher layers.

Attack Vector

The attack requires local access to the target device and the ability to initiate a firmware update process. An attacker crafts a malicious SB2 update file with carefully constructed header values that cause the parser to overflow internal buffers during the parsing phase. Because signature verification happens after parsing, the malicious data is processed before any authentication checks occur.

The attacker can use the buffer overflow to redirect execution flow, achieving code execution in the privileged bootloader context. This can be leveraged to extract cryptographic keys, disable security features, or execute arbitrary payloads on the microcontroller.

Detection Methods for CVE-2022-22819

Indicators of Compromise

• Unexpected firmware update attempts or bootloader activity on affected NXP microcontrollers
• Malformed SB2 files present on systems managing device firmware updates
• Anomalous device behavior following firmware update operations
• Evidence of memory corruption or unexpected code execution during boot sequences

Detection Strategies

• Implement file integrity monitoring on firmware update distribution systems to detect malicious SB2 files
• Monitor firmware update channels for unauthorized or malformed update packages
• Deploy network monitoring to detect unexpected firmware transfer activities to embedded devices
• Conduct hardware inventory audits to identify devices running vulnerable ROM version 1B

Monitoring Recommendations

• Establish baseline behavior for firmware update processes and alert on deviations
• Implement logging and alerting for all firmware update operations across device fleets
• Monitor for signs of bootloader-level code execution anomalies through device attestation mechanisms

How to Mitigate CVE-2022-22819

Immediate Actions Required

• Identify all deployed devices using affected NXP LPC55S66 and LPC55S69 microcontrollers with ROM version 1B
• Restrict physical and logical access to firmware update mechanisms on vulnerable devices
• Implement additional validation of SB2 files before they reach the bootloader parsing stage
• Contact NXP for device-specific guidance and potential ROM revision updates

Patch Information

Since this vulnerability exists in ROM code that cannot be modified after manufacturing, traditional software patches are not available for the affected ROM version 1B. Mitigation strategies must focus on preventing malicious SB2 files from reaching the vulnerable parser. Organizations should consult NXP's official resources for guidance on hardware revisions, ROM updates for new devices, or firmware-level workarounds that add pre-validation before invoking the ROM bootloader.

For detailed technical analysis of this vulnerability, refer to the Oxide Blog Vulnerability Analysis.

Workarounds

• Implement application-level SB2 file validation before passing updates to the bootloader
• Deploy firmware update proxy systems that verify SB2 file integrity and structure before forwarding to devices
• Use hardware security modules or trusted execution environments to pre-screen firmware updates
• Restrict firmware update capabilities to secure, authenticated channels with strict access controls

# Example: Restrict firmware update access on Linux-based management systems
# Limit access to firmware update tools to authorized administrators only
chmod 700 /usr/local/bin/nxp-firmware-update
chown root:admin /usr/local/bin/nxp-firmware-update

# Enable audit logging for firmware update operations
auditctl -w /usr/local/bin/nxp-firmware-update -p x -k firmware_update