# CVE-2025-40034: PCI/AER: Avoid NULL pointer dereference in aer_ratelimit()

> A missing NULL check in the Linux kernel PCI/AER driver allows a local attacker to cause a system crash via hardware error reporting.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Oct 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40034, DEBIAN-CVE-2025-40034, GHSA-4wjr-gmwc-pw8f, UBUNTU-CVE-2025-40034

## What is CVE-2025-40034?

CVE-2025-40034 is a vulnerability in Linux, published on 28 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:

PCI/AER: Avoid NULL pointer dereference in aer_ratelimit()

When platform firmware supplies error information to the OS, e.g., via the
ACPI APEI GHES mechanism, it may identify an error source device that
doesn't advertise an AER Capability and therefore dev->aer_info, which
contains AER stats and ratelimiting data, is NULL.

pci_dev_aer_stats_incr() already checks dev->aer_info for NULL, but
aer_ratelimit() did not, leading to NULL pointer dereferences like this one
from the URL below:

  {1}[Hardware Error]: Hardware error from APEI Generic Hardware Error Source: 0
  {1}[Hardware Error]: event severity: corrected
  {1}[Hardware Error]:   device_id: 0000:00:00.0
  {1}[Hardware Error]:   vendor_id: 0x8086, device_id: 0x2020
  {1}[Hardware Error]:   aer_cor_status: 0x00001000, aer_cor_mask: 0x00002000
  BUG: kernel NULL pointer dereference, address: 0000000000000264
  RIP: 0010:___ratelimit+0xc/0x1b0
  pci_print_aer+0x141/0x360
  aer_recover_work_func+0xb5/0x130

[8086:2020] is an Intel "Sky Lake-E DMI3 Registers" device that claims to
be a Root Port but does not advertise an AER Capability.

Add a NULL check in aer_ratelimit() to avoid the NULL pointer dereference.
Note that this also prevents ratelimiting these events from GHES.

[bhelgaas: add crash details to commit log]

## Which versions are affected by CVE-2025-40034?


## How do I fix CVE-2025-40034?

Apply the vendor's patch.

## Is CVE-2025-40034 being exploited?

There is no known exploitation of CVE-2025-40034 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40034 and fix it if it is affected.

What it is: CVE-2025-40034 is a vulnerability in Linux, published on 28 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-2025-40034 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-2025-40034/ (Markdown: https://insights.sbomify.com/CVE-2025-40034/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40034
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40034
- OSV: https://osv.dev/vulnerability/CVE-2025-40034

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40034/
Summaries are generated and may contain mistakes; the official description above is the record.