CVE-2022-30065: Busybox Use-After-Free Vulnerability

CVE-2022-30065 Overview

CVE-2022-30065 is a use-after-free vulnerability in BusyBox version 1.35.x's awk applet that can lead to denial of service and potentially arbitrary code execution. The vulnerability is triggered when processing a specially crafted awk pattern in the copyvar function. BusyBox is a widely deployed software suite providing common Unix utilities in a single executable, commonly used in embedded systems, IoT devices, and industrial control systems.

Critical Impact

This vulnerability allows local attackers to cause denial of service or potentially execute arbitrary code by convincing a user to process a malicious awk script, affecting embedded systems and industrial control infrastructure.

Affected Products

• BusyBox 1.35.0
• Siemens SCALANCE SC622-2C Firmware
• Siemens SCALANCE SC626-2C Firmware
• Siemens SCALANCE SC632-2C Firmware
• Siemens SCALANCE SC636-2C Firmware
• Siemens SCALANCE SC642-2C Firmware
• Siemens SCALANCE SC646-2C Firmware

Discovery Timeline

• May 18, 2022 - CVE-2022-30065 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2022-30065

Vulnerability Analysis

This use-after-free vulnerability (CWE-416) exists within the copyvar function of BusyBox's awk applet. Use-after-free vulnerabilities occur when memory is accessed after it has been freed, leading to undefined behavior. In this case, when the awk applet processes certain crafted patterns, it improperly references memory that has already been deallocated. This memory corruption can result in denial of service through application crashes, and under certain conditions, may allow an attacker to achieve code execution by manipulating the contents of the freed memory region before it is reused.

The vulnerability requires local access and user interaction—an attacker must convince a user or automated process to execute the awk applet with a malicious script. Given BusyBox's prevalence in embedded systems, IoT devices, and industrial control equipment like the affected Siemens SCALANCE series, the impact extends to critical infrastructure environments.

Root Cause

The root cause lies in improper memory management within the copyvar function of the awk applet. When processing specific awk patterns, the function fails to properly track memory allocation states, leading to a condition where a pointer to freed memory is subsequently dereferenced. This represents a classic use-after-free pattern where the application's memory lifecycle management does not correctly handle edge cases in pattern processing.

Attack Vector

The attack requires local access and user interaction. An attacker must craft a malicious awk pattern file and convince a target user or automated system to process it using BusyBox's awk applet. In embedded and IoT environments, this could potentially be achieved through:

• Uploading malicious configuration files that are processed by awk
• Exploiting web interfaces that allow file uploads processed by shell scripts
• Social engineering users to run awk on attacker-controlled input

When the crafted awk pattern is processed by the vulnerable copyvar function, memory corruption occurs. Depending on heap layout and timing, this can result in a crash (denial of service) or potentially allow the attacker to gain control of program execution flow.

The vulnerability mechanism involves the copyvar function improperly handling memory references during awk pattern processing. When specific pattern constructs are encountered, the function may free memory and subsequently attempt to access it, leading to use-after-free conditions. For detailed technical analysis, refer to the BusyBox Bug Report #14781.

Detection Methods for CVE-2022-30065

Indicators of Compromise

• Unexpected crashes or segmentation faults in BusyBox processes, particularly when executing awk operations
• Abnormal awk script files with unusual pattern constructs appearing on systems
• Core dumps from BusyBox indicating memory corruption in the awk applet
• Unusual process behavior following awk execution on embedded devices

Detection Strategies

• Monitor for BusyBox process crashes and analyze core dumps for evidence of use-after-free exploitation
• Implement file integrity monitoring on systems running BusyBox to detect unauthorized script uploads
• Deploy application-level monitoring to detect anomalous awk execution patterns
• Use memory sanitizers or security-enhanced builds of BusyBox in development and testing environments

Monitoring Recommendations

• Enable crash reporting and logging for BusyBox processes across embedded systems
• Monitor Siemens SCALANCE devices for unexpected service disruptions or reboots
• Implement network monitoring to detect potential malicious file uploads to affected devices
• Review system logs for repeated awk execution failures that may indicate exploitation attempts

How to Mitigate CVE-2022-30065

Immediate Actions Required

• Update BusyBox to a patched version that addresses CVE-2022-30065
• Apply firmware updates for affected Siemens SCALANCE devices as per the Siemens Security Advisory SSA-333517
• Restrict access to the awk applet on affected systems where possible
• Audit systems for BusyBox version 1.35.0 and prioritize remediation
• Implement network segmentation to limit exposure of vulnerable embedded devices

Patch Information

BusyBox maintainers have addressed this vulnerability in subsequent releases. Organizations should update to the latest stable version of BusyBox. For Siemens SCALANCE devices, consult the Siemens Security Advisory SSA-333517 for specific firmware versions containing the fix. The BusyBox Bug Report #14781 contains additional technical details about the patch.

Workarounds

• If the awk applet is not required, consider rebuilding BusyBox without awk support using the configuration option CONFIG_AWK=n
• Implement strict input validation and sanitization for any awk scripts processed on affected systems
• Restrict execution permissions for the awk applet to only trusted users and processes
• Deploy application whitelisting to prevent execution of unauthorized awk scripts

# Configuration example - Rebuild BusyBox without awk applet
# In BusyBox configuration (make menuconfig):
# Disable: Editors -> awk
# Or add to .config:
echo "CONFIG_AWK=n" >> .config
make oldconfig
make