# CVE-2025-39990: bpf: Check the helper function is valid in get_helper_proto

> A null pointer dereference in the Linux kernel BPF verifier can cause a system crash when specific configuration options are disabled.

- **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 Oct 2025
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-68519, BELL-CVE-2025-39990, DEBIAN-CVE-2025-39990, GHSA-2m9q-5w5g-jwfp, ROOT-OS-DEBIAN-11-CVE-2025-39990, ROOT-OS-DEBIAN-12-CVE-2025-39990, ROOT-OS-DEBIAN-13-CVE-2025-39990, ROOT-OS-UBUNTU-2204-CVE-2025-39990, ROOT-OS-UBUNTU-2404-CVE-2025-39990, UBUNTU-CVE-2025-39990

## What is CVE-2025-39990?

CVE-2025-39990 is a high-severity vulnerability in Linux, published on 15 Oct 2025. 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: Check the helper function is valid in get_helper_proto

kernel test robot reported verifier bug [1] where the helper func
pointer could be NULL due to disabled config option.

As Alexei suggested we could check on that in get_helper_proto
directly. Marking tail_call helper func with BPF_PTR_POISON,
because it is unused by design.

  [1] https://lore.kernel.org/oe-lkp/202507160818.68358831-lkp@intel.com

## Which versions are affected by CVE-2025-39990?


## How do I fix CVE-2025-39990?

Apply the vendor's patch.

## Is CVE-2025-39990 being exploited?

There is no known exploitation of CVE-2025-39990 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-39990 and fix it if it is affected.

What it is: CVE-2025-39990 is a high-severity vulnerability in Linux, published on 15 Oct 2025. 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-2025-39990 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-2025-39990/ (Markdown: https://insights.sbomify.com/CVE-2025-39990/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39990
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39990
- OSV: https://osv.dev/vulnerability/CVE-2025-39990

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39990/
Summaries are generated and may contain mistakes; the official description above is the record.