CVE-2022-49795 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
rethook: fix a potential memleak in rethook_alloc()
In rethook_alloc(), the variable rh is not freed or passed out if handler is NULL, which could lead to a memleak, fix it.
[Masami: Add "rethook:" tag to the title.]
Acke-by: Masami Hiramatsu (Google) <[email protected]>
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Analysis
by VulDB Data Team • 11/03/2025
The vulnerability identified as CVE-2022-49795 resides within the Linux kernel's rethook subsystem, specifically addressing a memory leak condition that could potentially impact system stability and resource management. This issue manifests in the rethook_alloc() function where improper memory handling occurs under specific error conditions. The rethook subsystem is designed to provide kernel-level hooking mechanisms that allow for interception and modification of function calls within the kernel, serving as a critical component for debugging, profiling, and security monitoring purposes. When the handler parameter is null during function execution, the allocated rethook structure fails to be properly deallocated or returned to the calling context, creating a memory leak scenario that accumulates over time.
The technical flaw stems from inadequate error handling within the rethook_alloc() function implementation. When the handler parameter evaluates to NULL, the function does not execute proper cleanup routines or return mechanisms for the allocated rethook structure referenced by the variable rh. This represents a classic memory management issue where allocated resources are not properly released, leading to memory leaks that can progressively consume system resources. The vulnerability demonstrates poor defensive programming practices where error conditions are not adequately considered during resource allocation and deallocation cycles. According to CWE classification, this corresponds to CWE-401: Improper Release of Memory Before Removing Last Reference, which specifically addresses memory leaks occurring due to failure to properly release allocated memory resources.
The operational impact of this memory leak vulnerability extends beyond simple resource consumption, potentially leading to system instability and performance degradation over extended periods of operation. As the memory leak accumulates through repeated calls to rethook_alloc() with NULL handlers, system memory becomes progressively consumed, which can eventually lead to memory pressure conditions that may cause system slowdowns or even system crashes. The vulnerability is particularly concerning in environments where kernel-level hooking is frequently utilized, such as security monitoring systems, debugging environments, or performance profiling tools that rely heavily on rethook functionality. The memory leak could be exploited in sustained attack scenarios where an adversary attempts to exhaust system resources through repeated triggering of the vulnerable code path, aligning with ATT&CK technique T1499.1 for resource exhaustion attacks.
Mitigation strategies for this vulnerability involve applying the kernel patch that properly handles the NULL handler case by ensuring that allocated memory is either freed or appropriately returned when the handler parameter is invalid. System administrators should prioritize updating their kernel versions to include the fix provided by the Linux kernel maintainers, which specifically addresses the memory leak by ensuring proper cleanup of rethook structures regardless of handler parameter values. Additionally, monitoring systems should be implemented to track memory usage patterns and identify potential memory leak conditions that may indicate exploitation attempts. The fix demonstrates proper resource management practices that align with secure coding guidelines, ensuring that all allocated resources are properly accounted for and released according to standard memory management protocols. Organizations should also consider implementing automated patch management systems to ensure timely application of security fixes across their kernel-based systems.