CVE-2025-40081 in Linux
Summary
by MITRE • 10/28/2025
In the Linux kernel, the following vulnerability has been resolved:
perf: arm_spe: Prevent overflow in PERF_IDX2OFF()
Cast nr_pages to unsigned long to avoid overflow when handling large AUX buffer sizes (>= 2 GiB).
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Analysis
by VulDB Data Team • 02/15/2026
The vulnerability identified as CVE-2025-40081 resides within the Linux kernel's performance monitoring subsystem, specifically affecting the ARM Scalable Performance Event (ARM_SPE) implementation. This issue manifests in the PERF_IDX2OFF() function which is responsible for calculating offsets within performance monitoring buffers. The flaw represents a classic integer overflow condition that can occur when processing auxiliary buffer sizes exceeding 2 gigabytes in magnitude. The vulnerability impacts systems utilizing ARM-based processors with performance monitoring capabilities, particularly those employing the ARM_SPE subsystem for detailed performance analysis and profiling operations.
The technical root cause of this vulnerability stems from an insufficient type casting operation within the PERF_IDX2OFF() function implementation. When the system processes auxiliary buffers with sizes greater than or equal to 2 gigabytes, the nr_pages parameter undergoes calculations that exceed the maximum representable value for its current data type. This overflow condition results in incorrect offset calculations that can lead to memory access violations, buffer overflows, or potentially arbitrary code execution within the kernel space. The issue specifically occurs during the conversion of page-based indexing to byte offsets, where the lack of proper unsigned long casting creates a scenario where large buffer sizes can wrap around to negative values or zero, effectively corrupting the buffer management logic. This type of vulnerability falls under CWE-191 Integer Underflow/Overflow, representing a fundamental weakness in numerical computation within kernel space operations.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially compromising system integrity and stability. Attackers could exploit this condition by crafting specific performance monitoring workloads that trigger the overflow scenario, potentially leading to privilege escalation or system crashes. Systems utilizing performance monitoring tools for profiling, debugging, or security analysis would be particularly vulnerable, as these tools frequently handle large buffer allocations. The vulnerability affects kernel versions where the ARM_SPE subsystem is enabled and actively used, making it relevant to embedded systems, servers, and mobile devices running Linux with ARM architecture. The exploitability of this issue is heightened in environments where performance monitoring is extensively utilized, as the overflow condition can be triggered through legitimate performance monitoring operations. This vulnerability aligns with ATT&CK technique T1059.003 Command and Scripting Interpreter: Windows Command Shell, as it represents a kernel-level code execution vector that could be leveraged to bypass security controls and escalate privileges.
Mitigation strategies for CVE-2025-40081 focus on implementing the recommended kernel patch that properly casts the nr_pages parameter to unsigned long type before performing offset calculations. System administrators should prioritize applying the latest kernel updates that contain this fix, particularly in production environments where performance monitoring is actively utilized. Additionally, monitoring for unusual performance monitoring behavior or buffer allocation patterns can serve as an early detection mechanism for potential exploitation attempts. The fix addresses the core mathematical operation by ensuring proper type handling and prevents the integer overflow from occurring in the first place. Organizations should also consider implementing kernel hardening measures such as stack canaries, kernel address space layout randomization, and other security mitigations that can further reduce the attack surface. Regular vulnerability assessments of kernel components and performance monitoring subsystems should be conducted to identify similar issues that may exist in other parts of the kernel codebase. The resolution of this vulnerability demonstrates the importance of proper type handling in kernel space operations and reinforces the need for comprehensive testing of edge cases involving large data structures and buffer management operations.