# CVE-2026-68330: net: airoha: Fix DMA direction for NPU mailbox buffer

> An attacker with local access could read stale data from the NPU mailbox buffer due to incorrect DMA direction handling on non-coherent architectures.

- **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:** 10 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-68330, DEBIAN-CVE-2026-68330, GHSA-r4m4-4ffx-qg5j, UBUNTU-CVE-2026-68330

## What is CVE-2026-68330?

CVE-2026-68330 is a high-severity vulnerability in Linux, published on 10 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:

net: airoha: Fix DMA direction for NPU mailbox buffer

airoha_npu_send_msg() always maps the mailbox buffer with DMA_TO_DEVICE,
but some callers expect the NPU to write response data back into the
same buffer:

- airoha_npu_wlan_msg_get() (NPU_OP_GET): NPU writes response into
  the buffer, then the caller reads it via memcpy()
- airoha_npu_ppe_stats_setup() (NPU_OP_SET): NPU writes back
  npu_stats_addr field in the response

On non-cache-coherent architectures like EN7581 (Cortex-A53 without
hardware cache coherency for NPU DMA), DMA_TO_DEVICE unmap is a no-op
— it does not invalidate the CPU cache. If the NPU-written cache line
is still present in the CPU cache when the caller reads the buffer,
the CPU observes stale data instead of the NPU response.

This is a timing-sensitive bug: small mailbox buffers (~24 bytes)
typically fit in a single cache line and may survive in the cache
until the caller reads them, producing silent data corruption rather
than a crash. The bug is more likely to trigger when the caller reads
the response immediately after dma_unmap_single() without intervening
cache-evicting operations.

Fix by using DMA_BIDIRECTIONAL for both map and unmap, which ensures
dma_unmap_single() invalidates the CPU cache on non-coherent systems.
The mailbox buffers are small so there is no performance concern.

## Which versions are affected by CVE-2026-68330?


## How do I fix CVE-2026-68330?

Apply the vendor's patch.

## Is CVE-2026-68330 being exploited?

There is no known exploitation of CVE-2026-68330 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68330 and fix it if it is affected.

What it is: CVE-2026-68330 is a high-severity vulnerability in Linux, published on 10 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-2026-68330 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-2026-68330/ (Markdown: https://insights.sbomify.com/CVE-2026-68330/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68330
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68330
- OSV: https://osv.dev/vulnerability/CVE-2026-68330

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68330/
Summaries are generated and may contain mistakes; the official description above is the record.