CVE-2022-48938 in Linux
Summary
by MITRE • 08/22/2024
In the Linux kernel, the following vulnerability has been resolved:
CDC-NCM: avoid overflow in sanity checking
A broken device may give an extreme offset like 0xFFF0 and a reasonable length for a fragment. In the sanity check as formulated now, this will create an integer overflow, defeating the sanity check. Both offset and offset + len need to be checked in such a manner that no overflow can occur. And those quantities should be unsigned.
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Analysis
by VulDB Data Team • 11/20/2024
The vulnerability identified as CVE-2022-48938 affects the Linux kernel's implementation of the CDC-NCM (Communications Device Class - Network Control Model) driver, which is responsible for handling network communication through USB devices. This issue represents a critical security flaw that undermines the integrity of input validation mechanisms within the kernel's network subsystem. The vulnerability specifically manifests in the sanity checking logic that validates fragment offsets and lengths during USB network packet processing, creating a potential pathway for malicious actors to bypass security controls through carefully crafted malformed input data.
The technical flaw stems from inadequate integer overflow protection in the validation routines of the CDC-NCM driver implementation. When a malicious or malfunctioning USB device attempts to communicate with a Linux system, it may provide an extreme offset value such as 0xFFF0 combined with a reasonable length parameter for a network fragment. The current sanity check implementation fails to properly validate these values, allowing the arithmetic operation of offset plus length to overflow beyond the maximum representable value for signed integers. This overflow effectively neutralizes the intended validation mechanism, enabling attackers to craft packets that appear valid to the kernel's sanity checks while actually containing malformed data that could be exploited for further attacks.
This vulnerability directly relates to CWE-191, Integer Underflow/Overflow, which describes the condition where integer arithmetic operations produce results that exceed the maximum or minimum values representable by the data type. The flaw demonstrates how improper input validation can lead to security bypasses, particularly in kernel-level network drivers where malicious input can potentially escalate to system compromise. From an operational perspective, this vulnerability could be exploited by attackers who gain physical access to a target system or who can induce a device to connect to a system through USB ports, potentially leading to privilege escalation or denial of service conditions. The impact extends beyond simple data corruption as it represents a fundamental breakdown in the kernel's ability to validate incoming network data, which is critical for maintaining system integrity and security boundaries.
The mitigation approach for CVE-2022-48938 requires implementing proper unsigned integer validation for both offset and length parameters, ensuring that arithmetic operations cannot produce overflow conditions that would defeat the sanity checks. This involves modifying the kernel code to perform explicit validation of the offset plus length calculation using unsigned integer types, thereby preventing the overflow that currently allows malicious inputs to bypass validation. Additionally, the fix should enforce bounds checking that accounts for potential integer overflows by using appropriate mathematical operations or alternative validation approaches that do not rely on arithmetic operations that could overflow. System administrators should ensure their Linux kernels are updated to versions containing the patched implementation, as this vulnerability affects the core networking capabilities of Linux systems and could potentially be exploited in scenarios involving USB network devices, including smartphones, tablets, and other USB network adapters. The fix aligns with ATT&CK technique T1059.007 for privilege escalation through kernel exploits and represents a critical security patch that addresses fundamental input validation weaknesses in kernel network drivers that could enable broader attack vectors.