Linux EUVD-2026-18198

The vulnerability resides in the Linux kernel's memory sealing (mseal) subsystem, specifically in the virtual memory area (VMA) iteration logic used to apply seal flags across a range of memory. The mseal feature is a security mechanism that prevents processes from modifying memory protections on sealed regions. The root cause is a state-tracking bug where the code caches the end boundary of the current VMA (curr_end) but fails to update this value when vma_modify_flags() performs a VMA merge operation. When the loop advances by setting curr_start = curr_end, it uses stale boundary data, leading to incorrect VMA ranges being processed. The fix consolidates boundary tracking by unconditionally updating curr_end to vma->vm_end after each iteration and converting curr_start and curr_end to const values clamped to both the input range and individual VMA extents, eliminating the class of state-consistency bugs entirely.