# CVE-2026-74338: bpf: Reject sleepable BPF_LSM_CGROUP programs at load time

> A local attacker can cause a kernel crash by loading a sleepable BPF LSM cgroup program that attempts to sleep in an atomic context.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 21 Oct 2026
- **Also known as:** AZL-96018, BELL-CVE-2026-74338, DEBIAN-CVE-2026-74338, GHSA-rqq6-3pqg-qxx2, UBUNTU-CVE-2026-74338

## What is CVE-2026-74338?

CVE-2026-74338 is a high-severity denial of service 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: Reject sleepable BPF_LSM_CGROUP programs at load time

The cgroup shim runs under rcu_read_lock_dont_migrate(), so we should
not attach any sleepable BPF programs there. Add support to the verifier
to explicitly reject attempts to load sleepable BPF programs destined
for LSM cgroup attachment.

Without this, we get the following splat from a BPF_LSM_CGROUP
program marked BPF_F_SLEEPABLE attached to file_open when it calls
bpf_get_dentry_xattr():

  BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:1567
  in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 34317, name: load
  preempt_count: 0, expected: 0
  RCU nest depth: 2, expected: 0
  Call Trace:
   down_read+0x76/0x480
   ext4_xattr_get+0x11f/0x700
   __vfs_getxattr+0xf0/0x150
   bpf_get_dentry_xattr+0xbb/0xf0
   bpf_prog_e76a298dac9218c6_test_open+0x6a/0x85
   __cgroup_bpf_run_lsm_current+0x326/0x840
   bpf_trampoline_6442534646+0x62/0x14d
   security_file_open+0x34/0x60
   do_dentry_open+0x340/0x1260
   vfs_open+0x7a/0x440
   path_openat+0x1bac/0x30a0

libbpf provides a .s named section variant for every sleepable
program type except lsm_cgroup, reflecting that per-cgroup LSM programs
are intended to only run in a non-sleepable context.

The above splat was obtained by bypassing libbpf by using bpf(2)
directly.

## Which versions are affected by CVE-2026-74338?


## How do I fix CVE-2026-74338?

Apply the vendor's patch.

## Is CVE-2026-74338 being exploited?

There is no known exploitation of CVE-2026-74338 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74338 and fix it if it is affected.

What it is: CVE-2026-74338 is a high-severity denial of service 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-2026-74338 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-2026-74338/ (Markdown: https://insights.sbomify.com/CVE-2026-74338/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74338
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74338
- OSV: https://osv.dev/vulnerability/CVE-2026-74338

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74338/
Summaries are generated and may contain mistakes; the official description above is the record.