CVE-2024-36891 in Linux
Summary
by MITRE • 05/30/2024
In the Linux kernel, the following vulnerability has been resolved:
maple_tree: fix mas_empty_area_rev() null pointer dereference
Currently the code calls mas_start() followed by mas_data_end() if the maple state is MA_START, but mas_start() may return with the maple state node == NULL. This will lead to a null pointer dereference when checking information in the NULL node, which is done in mas_data_end().
Avoid setting the offset if there is no node by waiting until after the maple state is checked for an empty or single entry state.
A user could trigger the events to cause a kernel oops by unmapping all vmas to produce an empty maple tree, then mapping a vma that would cause the scenario described above.
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Analysis
by VulDB Data Team • 08/28/2025
The vulnerability described in CVE-2024-36891 represents a critical null pointer dereference flaw within the Linux kernel's maple tree implementation that could lead to system instability and potential privilege escalation. This issue specifically affects the mas_empty_area_rev() function which handles reverse empty area operations within the maple tree data structure used for memory management. The vulnerability stems from improper state handling during memory mapping operations where the kernel fails to properly validate the existence of a tree node before attempting to access its properties. According to CWE-476, this constitutes a null pointer dereference vulnerability that occurs when a program attempts to access memory through a pointer that has not been properly initialized or has been set to null. The flaw exists in the kernel's memory management subsystem and directly impacts the stability of the operating system when processing memory mapping operations.
The technical execution of this vulnerability occurs through a specific sequence of operations that manipulate the maple tree state machine. When the maple state is set to MA_START, the code invokes mas_start() which may legitimately return with a node pointer set to NULL, indicating an empty or uninitialized state. However, the subsequent call to mas_data_end() does not properly account for this null condition, leading to immediate dereference of the NULL node pointer. This creates a classic null pointer dereference scenario where the kernel attempts to access memory locations through a null reference, resulting in a kernel oops or system crash. The vulnerability manifests when a user-space process triggers a sequence of memory unmapping operations that result in an empty maple tree, followed by mapping operations that place the tree in a state where the null pointer dereference is triggered. The ATT&CK framework categorizes this as a privilege escalation technique through kernel exploitation, as the vulnerability allows an attacker to cause system instability that could potentially be leveraged for further exploitation.
The operational impact of CVE-2024-36891 extends beyond simple system crashes to potentially enable more sophisticated attack vectors within kernel space. When the kernel encounters this null pointer dereference, it generates a kernel oops message and typically results in a system panic or reboot, causing denial of service conditions that could be exploited by malicious actors to disrupt system availability. The vulnerability affects the kernel's memory management subsystem and could theoretically be combined with other exploits to achieve privilege escalation or bypass security controls. The specific conditions required to trigger this vulnerability involve manipulating virtual memory areas through mmap and munmap system calls, creating a scenario where the maple tree transitions through states that expose the null pointer access issue. System administrators and security professionals should be particularly concerned about this vulnerability as it represents an exploitable kernel flaw that could be leveraged in targeted attacks against systems running affected kernel versions. The vulnerability demonstrates the critical importance of proper state validation in kernel code and highlights the need for comprehensive testing of edge cases in memory management subsystems. Mitigation efforts should focus on applying the kernel patch that addresses the null pointer dereference by ensuring proper validation of node pointers before accessing their properties, thereby preventing the kernel from attempting to dereference null references during maple tree operations.