CVE-2023-0459

What it actually does

The flaw bypasses access_ok checks in copy_from_user on 64-bit Linux kernels by omitting __uaccess_begin_nospec, allowing a local user to supply a kernel pointer and read kernel memory contents.

Why it matters to the business

On affected Linux systems this can expose sensitive kernel data to local users, increasing risk of further attacks or data leakage in environments running unpatched kernels; low EPSS and no KEV status indicate limited observed exploitation after 1231 days.

How an attack unfolds

A local attacker identifies a vulnerable kernel build, invokes copy_from_user with a crafted kernel address that evades the missing nospec barrier, and reads arbitrary kernel memory to obtain information useful for additional exploits.

How to fix it

Upgrade the Linux kernel to commit 4b842e4e25b12951fa10dedb4bc16bc47e3b850c or later; rebuild and reboot affected systems with the patched kernel.

How to confirm the fix worked

Verify the running kernel git commit or version string contains 4b842e4e25b12951fa10dedb4bc16bc47e3b850c; confirm access_ok now properly gates copy_from_user calls with nospec.

Typical attack path

1. Gain local user access on a 64-bit Linux system
2. Confirm presence of the vulnerable kernel commit before 4b842e4e25b12951fa10dedb4bc16bc47e3b850c
3. Invoke copy_from_user with a kernel pointer that bypasses access_ok
4. Read and exfiltrate kernel memory contents

How to detect it

Review local process execution and kernel audit logs for unusual memory-access patterns or repeated copy_from_user attempts targeting high kernel addresses; correlate with threat actor mentions of Linux kernel information disclosure activity.

What your security team should do

• Prioritize kernel upgrade to the fixed commit on all affected systems
• Enforce least-privilege access to limit local user exposure
• Monitor kernel update channels for downstream distribution patches