CVE-2025-21932 is a vulnerability in the Linux kernel's memory management subsystem where an out-of-memory failure during a virtual memory area (VMA) merge operation can leave internal state inconsistent. This inconsistency can cause subsequent operations on VMAs to use invalid start and end values, potentially leading to kernel instability or crashes. The issue arises in the vma_modify() function when a merge attempt fails due to memory allocation failure, but the VMA state is partially updated nonetheless. The vulnerability was reported by syzkaller and Brad Spengler and is triggered during madvise() system calls that span multiple VMAs. While the scenario is theoretically possible, it is considered unlikely in practice due to kernel memory reclaim behavior. The fix involves aborting the operation early when memory allocation fails during merge attempts to maintain consistent VMA state.