CVE-2026-63873 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
accel/amdxdna: Fix mm_struct reference leak in aie2_populate_range()
aie2_populate_range() jumps back to the again label without calling mmput(mm), leaking a reference to the mm_struct.
Add the missing mmput() before jumping to again.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability identified in the Linux kernel's amdxdna driver represents a critical memory management issue that could lead to system instability and resource exhaustion. This flaw exists within the aie2_populate_range() function where improper reference counting handling creates a memory leak scenario. The specific technical implementation error occurs when the function executes a jump back to the again label without properly releasing the mm_struct reference through the mmput() function call.
The root cause of this vulnerability stems from inadequate resource management practices within kernel space code execution. When the aie2_populate_range() function encounters certain conditions during memory range population operations, it performs an unconditional jump to the again label without executing the necessary cleanup routine that would decrement the reference count of the mm_struct. This reference leak directly violates fundamental kernel memory management principles and creates a persistent resource consumption problem that accumulates over time.
From an operational perspective, this vulnerability presents significant risks to system stability and performance across Linux systems utilizing AMD XDNA hardware acceleration capabilities. The continuous leakage of mm_struct references can eventually lead to memory exhaustion conditions where the kernel cannot allocate additional memory mappings for legitimate processes. This type of resource leak directly impacts system availability and could be exploited by malicious actors to perform denial-of-service attacks against systems running affected kernel versions.
The technical flaw aligns with CWE-401, which specifically addresses improper release of memory after transfer of ownership, and demonstrates a classic case of reference counting error in kernel space programming. This vulnerability also maps to ATT&CK technique T1499.004, which covers "File System Wipeout" through resource exhaustion attacks that could be facilitated by this memory leak condition. The impact extends beyond simple memory consumption as it affects the overall kernel memory management subsystem and can cascade into broader system stability issues.
The recommended mitigation strategy involves implementing the straightforward fix of adding the missing mmput() call before any jump to the again label within the aie2_populate_range() function. This correction ensures proper reference counting and prevents the accumulation of leaked mm_struct references. System administrators should prioritize applying this kernel patch across all affected deployments, particularly in server environments where continuous operation and resource efficiency are critical. The fix represents a minimal code change that addresses the root cause without introducing compatibility risks or performance degradation to existing functionality.
This vulnerability exemplifies the importance of rigorous code review processes for kernel space modifications and highlights the critical nature of proper reference counting in memory management operations. The issue demonstrates how seemingly minor oversights in resource cleanup can create significant long-term stability problems in operating system kernels where reliability is paramount. Regular security auditing of kernel subsystems, particularly those handling hardware acceleration capabilities, remains essential to identify and remediate similar reference counting vulnerabilities before they can be exploited in production environments.