# CVE-2026-43466: net/mlx5e: Fix DMA FIFO desync on error CQE SQ recovery

> A race condition in the mlx5e driver causes DMA FIFO desync, leading to kernel warnings and potential denial of service.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43466, DEBIAN-CVE-2026-43466, GHSA-757p-mh2f-rf8w, ROOT-OS-DEBIAN-11-CVE-2026-43466, ROOT-OS-UBUNTU-2204-CVE-2026-43466, ROOT-OS-UBUNTU-2404-CVE-2026-43466, UBUNTU-CVE-2026-43466

## What is CVE-2026-43466?

CVE-2026-43466 is a high-severity vulnerability in Linux kernel, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5e: Fix DMA FIFO desync on error CQE SQ recovery

In case of a TX error CQE, a recovery flow is triggered,
mlx5e_reset_txqsq_cc_pc() resets dma_fifo_cc to 0 but not dma_fifo_pc,
desyncing the DMA FIFO producer and consumer.

After recovery, the producer pushes new DMA entries at the old
dma_fifo_pc, while the consumer reads from position 0.
This causes us to unmap stale DMA addresses from before the recovery.

The DMA FIFO is a purely software construct with no HW counterpart.
At the point of reset, all WQEs have been flushed so dma_fifo_cc is
already equal to dma_fifo_pc. There is no need to reset either counter,
similar to how skb_fifo pc/cc are untouched.

Remove the 'dma_fifo_cc = 0' reset.

This fixes the following WARNING:
    WARNING: CPU: 0 PID: 0 at drivers/iommu/dma-iommu.c:1240 iommu_dma_unmap_page+0x79/0x90
    Modules linked in: mlx5_vdpa vringh vdpa bonding mlx5_ib mlx5_vfio_pci ipip mlx5_fwctl tunnel4 mlx5_core ib_ipoib geneve ip6_gre ip_gre gre nf_tables ip6_tunnel rdma_ucm ib_uverbs ib_umad vfio_pci vfio_pci_core act_mirred act_skbedit act_vlan vhost_net vhost tap ip6table_mangle ip6table_nat ip6table_filter ip6_tables iptable_mangle cls_matchall nfnetlink_cttimeout act_gact cls_flower sch_ingress vhost_iotlb iptable_raw tunnel6 vfio_iommu_type1 vfio openvswitch nsh rpcsec_gss_krb5 auth_rpcgss oid_registry xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink iptable_nat nf_nat xt_addrtype br_netfilter overlay zram zsmalloc rpcrdma ib_iser libiscsi scsi_transport_iscsi rdma_cm iw_cm ib_cm ib_core fuse [last unloaded: nf_tables]
    CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.13.0-rc5_for_upstream_min_debug_2024_12_30_21_33 #1
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
    RIP: 0010:iommu_dma_unmap_page+0x79/0x90
    Code: 2b 4d 3b 21 72 26 4d 3b 61 08 73 20 49 89 d8 44 89 f9 5b 4c 89 f2 4c 89 e6 48 89 ef 5d 41 5c 41 5d 41 5e 41 5f e9 c7 ae 9e ff <0f> 0b 5b 5d 41 5c 41 5d 41 5e 41 5f c3 66 2e 0f 1f 84 00 00 00 00
    Call Trace:
     <IRQ>
     ? __warn+0x7d/0x110
     ? iommu_dma_unmap_page+0x79/0x90
     ? report_bug+0x16d/0x180
     ? handle_bug+0x4f/0x90
     ? exc_invalid_op+0x14/0x70
     ? asm_exc_invalid_op+0x16/0x20
     ? iommu_dma_unmap_page+0x79/0x90
     ? iommu_dma_unmap_page+0x2e/0x90
     dma_unmap_page_attrs+0x10d/0x1b0
     mlx5e_tx_wi_dma_unmap+0xbe/0x120 [mlx5_core]
     mlx5e_poll_tx_cq+0x16d/0x690 [mlx5_core]
     mlx5e_napi_poll+0x8b/0xac0 [mlx5_core]
     __napi_poll+0x24/0x190
     net_rx_action+0x32a/0x3b0
     ? mlx5_eq_comp_int+0x7e/0x270 [mlx5_core]
     ? notifier_call_chain+0x35/0xa0
     handle_softirqs+0xc9/0x270
     irq_exit_rcu+0x71/0xd0
     common_interrupt+0x7f/0xa0
     </IRQ>
     <TASK>
     asm_common_interrupt+0x22/0x40

Weakness: CWE-662 (Improper Synchronization)

## Which versions are affected by CVE-2026-43466?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43466?

Apply the vendor's patch.

## Is CVE-2026-43466 being exploited?

There is no known exploitation of CVE-2026-43466 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43466 and fix it if it is affected.

What it is: CVE-2026-43466 is a high-severity vulnerability in Linux kernel, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43466 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-43466/ (Markdown: https://insights.sbomify.com/CVE-2026-43466/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43466
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43466
- OSV: https://osv.dev/vulnerability/CVE-2026-43466

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43466/
Summaries are generated and may contain mistakes; the official description above is the record.