CVE-2024-53066

What it actually does

Uninitialized mdsthreshold field in nfs_fattr structure leads to use of uninitialized value when decode_attr_mdsthreshold is called during NFSv4 getattr decoding.

Why it matters to the business

Linux systems performing NFSv4 operations may experience kernel warnings or instability; the flaw affects many distributions using the affected kernel versions and requires prompt patching to maintain stability.

How an attack unfolds

An attacker with network access to an NFSv4 server triggers repeated getattr operations on files or directories, causing the kernel to process responses that reach the uninitialized mdsthreshold path in decode_getfattr_attrs and potentially leak or corrupt memory.

How to fix it

Upgrade the Linux kernel to a version containing commit 25ffd294fef81a7f3cd9528adf21560c04d98747 or later; rebuild and reboot affected systems, ensuring nfs_fattr_init properly zeros mdsthreshold.

How to confirm the fix worked

Confirm the fix by checking that nfs_fattr_init initializes mdsthreshold to NULL, then re-run KMSAN or similar dynamic analysis tools on NFS getattr workloads to verify absence of uninit-value warnings.

Typical attack path

1. Establish NFSv4 mount or connection to target system
2. Perform file attribute lookups via vfs_statx or similar syscalls that invoke nfs4_proc_getattr
3. Trigger decode_getfattr_generic path that calls decode_attr_mdsthreshold on uninitialized data
4. Observe or exploit resulting uninitialized memory access

How to detect it

Search kernel logs and audit trails for KMSAN uninit-value reports mentioning decode_getfattr_attrs or nfs4_xdr_dec_getattr; correlate with NFSv4 traffic and process activity involving cp, stat, or path lookups.

What your security team should do

• Apply the referenced kernel commit or distribution update immediately on all NFSv4 clients and servers
• Monitor kernel logs for KMSAN or similar uninitialized-value reports during NFS activity
• Prioritize patching on internet-facing or high-value NFS deployments given listed threat actor interest in Linux kernel memory issues