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.
- 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
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.
Sources
Also known as BELL-CVE-2026-68330, DEBIAN-CVE-2026-68330, GHSA-r4m4-4ffx-qg5j, UBUNTU-CVE-2026-68330.