CVE-2021-47122 in Linux
Summary
by MITRE • 03/15/2024
In the Linux kernel, the following vulnerability has been resolved:
net: caif: fix memory leak in caif_device_notify
In case of caif_enroll_dev() fail, allocated link_support won't be assigned to the corresponding structure. So simply free allocated pointer in case of error
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/04/2025
The vulnerability identified as CVE-2021-47122 represents a memory leak flaw within the Linux kernel's CAIF network subsystem. This issue specifically affects the caif_device_notify function which handles device notification events for the CAIF (Cellular Advanced Functionality) protocol implementation. The CAIF protocol is designed to provide advanced cellular communication capabilities and is part of the Linux kernel's networking stack. The vulnerability stems from improper memory management during device enrollment operations, where allocated memory structures are not correctly freed when enrollment fails.
The technical flaw manifests in the caif_enroll_dev() function where memory allocation occurs for link_support structures but fails to properly handle cleanup when the enrollment process encounters errors. This creates a memory leak scenario where allocated memory remains unreleased in the kernel's memory pool. The issue is particularly significant because it occurs within kernel space, meaning that persistent memory leaks can lead to gradual system resource exhaustion and potential denial of service conditions. The vulnerability is classified under CWE-401 as a failure to release memory allocated to a resource, which directly impacts system stability and performance. The flaw represents a classic case of resource management error where allocated resources are not properly deallocated upon error conditions, leading to memory fragmentation and potential system instability.
The operational impact of this vulnerability extends beyond simple memory consumption issues. When the CAIF subsystem is actively managing cellular network connections, repeated failures in device enrollment can lead to progressive memory depletion, eventually causing system slowdowns or complete system crashes. This is particularly concerning in embedded systems or mobile devices where memory resources are constrained and system reliability is critical. The vulnerability can be exploited by malicious actors who intentionally trigger device enrollment failures to consume system memory resources, potentially leading to denial of service attacks against cellular communication services. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1499.004 which involves resource exhaustion attacks targeting system memory, and T1566.001 which covers social engineering attacks that could manipulate system resources. The vulnerability affects all Linux kernel versions that implement the CAIF network protocol and are susceptible to memory leak exploitation through improper error handling.
Mitigation strategies for CVE-2021-47122 focus on implementing proper error handling and resource cleanup mechanisms within the kernel code. The fix involves ensuring that allocated link_support structures are properly freed when caif_enroll_dev() fails, preventing memory leaks from occurring. System administrators should prioritize updating to kernel versions that include the patched implementation, as this vulnerability cannot be effectively mitigated through configuration changes alone. Monitoring systems for memory usage patterns and implementing automated alerts for unusual memory consumption can help detect exploitation attempts. The patch addresses the root cause by ensuring that all allocated memory paths properly handle error conditions, which aligns with secure coding practices outlined in the CERT Secure Coding Standards for kernel development. Organizations should also implement regular kernel updates and security assessments to prevent similar memory management issues from occurring in other subsystems, as memory leaks represent one of the most persistent and dangerous classes of vulnerabilities in operating system kernels.