CVE-2025-21851: Linux Kernel

Low severity, CVSS 3.3. EPSS: 0.2% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix softlockup in arena_map_free on 64k page kernel On an aarch64 kernel with CONFIG_PAGE_SIZE_64KB=y, arena_htab tests cause a segmentation fault and soft lockup. The same failure is not observed with 4k pages on aarch64. It turns out arena_map_free() is calling apply_to_existing_page_range() with the address returned by bpf_arena_get_kern_vm_start(). If this address is not page-aligned the code ends up calling apply_to_pte_range() with that unaligned address causing soft lockup. Fix it by round up GUARD_SZ to PAGE_SIZE << 1 so that the division by 2 in bpf_arena_get_kern_vm_start() returns a page-aligned value.

Affected products

• Linux Linux Kernel: from 6.9, before 6.12.17 (fixed in 6.12.17); from 6.13, before 6.13.5 (fixed in 6.13.5); version 6.9 only; version 6.14 only

Published 2025-03-12. Last modified 2026-07-30.