# CVE-2026-74315: lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()

> An attacker can read uninitialized kernel memory via NLMv4 file handle hashing, potentially leaking sensitive data.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-74315, GHSA-5v8r-fj78-ffg6, UBUNTU-CVE-2026-74315

## What is CVE-2026-74315?

CVE-2026-74315 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

## Which versions are affected by CVE-2026-74315?


## How do I fix CVE-2026-74315?

Apply the vendor's patch.

## Is CVE-2026-74315 being exploited?

There is no known exploitation of CVE-2026-74315 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74315 and fix it if it is affected.

What it is: CVE-2026-74315 is a critical vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74315 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-74315/ (Markdown: https://insights.sbomify.com/CVE-2026-74315/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74315
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74315
- OSV: https://osv.dev/vulnerability/CVE-2026-74315

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74315/
Summaries are generated and may contain mistakes; the official description above is the record.