CVE-2024-0775

What it actually does

Use-after-free in __ext4_remount during ext4 remount handling frees old quota file names before a potential failure path, allowing a local process to read kernel memory that was previously freed.

Why it matters to the business

Local attackers on affected Linux systems can leak kernel memory contents, which may expose sensitive data and enable escalation to more serious attacks; the issue affects any organization running unpatched kernels with ext4 filesystems.

How an attack unfolds

An attacker with local access triggers a crafted ext4 remount sequence that hits the failure path in quota name handling, then reuses the freed memory to read residual kernel data; the described threat actor context centers on Linux kernel use-after-free techniques.

How to fix it

Upgrade the Linux kernel to the commit 6995e2de6891c724bfeb2db33d7b87775f913ad1 or later; apply the vendor-supplied patch for the affected distribution and reboot into the fixed kernel.

How to confirm the fix worked

Verify the running kernel contains commit 6995e2de6891c724bfeb2db33d7b87775f913ad1 or the equivalent distribution backport; attempt a controlled remount on an ext4 volume with quotas and confirm no use-after-free behavior via kernel debugging tools.

Typical attack path

1. Obtain local user access on a target Linux system
2. Mount or prepare an ext4 filesystem with quota enabled
3. Issue a remount operation engineered to reach the failure path in __ext4_remount
4. Read the use-after-free memory region to extract kernel information
5. Leverage disclosed data for further privilege escalation or information gathering

How to detect it

Review kernel logs for ext4 remount-related warnings or oops messages around the time of suspicious local activity; examine audit logs for unusual mount/remount commands issued by non-administrative users.

What your security team should do

• Immediately identify all systems running affected kernel versions and schedule patching
• Prioritize systems with ext4 filesystems and quota support
• Monitor for local privilege-escalation attempts while patches are applied
• Update kernel packages across the fleet and verify the fixed commit is present