Linux Kernel lockd nlm4svc_lookup_file uninitialized pointer

Summaryinfo

A vulnerability was found in Linux Kernel and classified as very critical. Affected is the function nlm4svc_lookup_file of the component lockd. Executing a manipulation can lead to uninitialized pointer. This vulnerability appears as CVE-2026-74315. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel (the affected version is unknown). This vulnerability affects the function nlm4svc_lookup_file of the component lockd. The manipulation with an unknown input leads to a uninitialized pointer vulnerability. The CWE definition for the vulnerability is CWE-824. The product accesses or uses a pointer that has not been initialized. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file() file_hash() digests the first LOCKD_FH_HASH_SIZE bytes of nfs_fh.data when bucketing nlm_files[], independent of fh.size. Commit 3de744ee4e45 ("lockd: Use xdrgen XDR functions for the NLMv4 TEST procedure") set .pc_argzero to zero for the converted procedures and moved file-handle population into nlm4svc_lookup_file(), which copies only xdr_lock->fh.len bytes into lock->fh.data. When an NLMv4 client presents a file handle shorter than LOCKD_FH_HASH_SIZE, bytes fh.len..31 retain whatever the argument buffer held from an earlier request. The same wire handle then hashes to different buckets across calls; nlm_lookup_file() misses the existing nlm_file entry, and lock-state lookups fail. Zero only the tail bytes that file_hash() would otherwise consume. Handles of LOCKD_FH_HASH_SIZE or larger already populate every byte that file_hash() reads.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-74315 since 08/15/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/15/2026).

Applying the patch 686c2434f9f16b87aeed18d76cc562df9f2695ab/6e4c62caecf792e8a15ad9bc7f371e57c17e3302 is able to eliminate this problem.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

License

• open-source

Website

• Vendor: https://www.kernel.org/

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