CVE-2023-53989: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53989 is a vulnerability in the Linux kernel's arm64 memory management subsystem involving an incorrect VA-range sanity check in create_mapping_noalloc() and update_mapping_prot(). The flaw stems from a historically incorrect boundary condition that was introduced when the kernel VA space was flipped for arm64, causing the check to incorrectly flag or permit operations on the KASAN shadow region or module region. It was published on December 24, 2025, and has a CVE status of "Deferred" with an estimated CVSS severity of Medium (Feedly, CVE.org).

The root cause is an improper boundary check (related to CWE-697: Incorrect Comparison) in the arm64 memory mapping functions create_mapping_noalloc() and update_mapping_prot(). The original sanity check if (virt >= PAGE_END && virt < VMALLOC_START) was intended to warn when a virtual address would not be translated via TTBR1, but after the kernel VA space flip introduced in commit 14c127c957c1c607 ("arm64: mm: Flip kernel VA space"), the condition became logically incorrect — it could only be true for the KASAN shadow or module regions, which are valid targets for mapping operations. The fix corrects the condition to accurately reflect the current VA layout, preventing spurious warnings or silent early returns that could mask legitimate mapping failures (Feedly).

The incorrect sanity check could cause create_mapping_noalloc() or update_mapping_prot() to silently return early when operating on valid kernel VA regions such as the KASAN shadow or module region, potentially resulting in incomplete or missing memory mappings. This could lead to kernel instability, incorrect memory protection attributes being applied, or subtle memory safety issues on arm64 systems. The impact is primarily an availability and integrity concern at the kernel level, with no direct user-space data exposure pathway identified (Feedly).

The fix has been applied to the Linux kernel stable tree via multiple commits (e.g., 9d8d3df71516, 32020fc2a837, 621619f626cb, ab9b40080929, b03c7fcc5ed8). Users running arm64 Linux systems should update to a patched kernel version that includes these fixes. SUSE has issued advisories (SUSE-2026-0281-1 and SUSE-2026-20876-1) incorporating the fix for affected kernel packages (Feedly, Linux Security).