# CVE-2026-74400: bpf: fix crash in bpf_[set|remove]_dentry_xattr for negative dentries

> A local attacker can trigger a kernel crash via BPF kfuncs by passing negative dentries, causing a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-74400, DEBIAN-CVE-2026-74400, GHSA-vrq8-fr7j-453w, UBUNTU-CVE-2026-74400

## What is CVE-2026-74400?

CVE-2026-74400 is a vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

bpf: fix crash in bpf_[set|remove]_dentry_xattr for negative dentries

bpf_set_dentry_xattr and bpf_remove_dentry_xattr BPF kfuncs attempt to
lock the inode of the supplied dentry without checking if it is
NULL. If a negative dentry is passed (e.g. from
security_inode_create), d_inode(dentry) returns NULL, and
inode_lock(inode) will cause a NULL pointer dereference.

Trivially fix this by adding a NULL check for inode before attempting
to lock it, returning -EINVAL if it is NULL.

Additionally, drop WARN_ON(!inode) in bpf_xattr_read_permission() and
bpf_xattr_write_permission(). These warnings could be triggered by
passing a negative dentry to bpf_get_dentry_xattr() or the _locked
variants of the xattr kfuncs, potentially causing a Denial of Service
on systems with panic_on_warn enabled. Instead, simply return -EINVAL.

## Which versions are affected by CVE-2026-74400?


## How do I fix CVE-2026-74400?

Apply the vendor's patch.

## Is CVE-2026-74400 being exploited?

There is no known exploitation of CVE-2026-74400 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74400 and fix it if it is affected.

What it is: CVE-2026-74400 is a vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74400 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-2026-74400/ (Markdown: https://insights.sbomify.com/CVE-2026-74400/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74400
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74400
- OSV: https://osv.dev/vulnerability/CVE-2026-74400

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74400/
Summaries are generated and may contain mistakes; the official description above is the record.