---
id: "CVE-2026-98791"
kind: "vulnerability"
aliases: ["CVE-2026-98791"]
title: "Linux kernel: mlx5 AF_XDP teardown can crash the system via NULL dereference"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["af_xdp", "infrastructure", "kernel", "linux", "mellanox", "mlx5", "nvidia"]
not_affected_if: ["no-af_xdp-sockets", "no-mlx5-hardware", "no-tx-timestamping"]
published_at: "2026-10-18T16:17:33+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:15:15+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98791", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: mlx5 AF_XDP teardown can crash the system via NULL dereference

During teardown of an AF_XDP transmit queue on Mellanox mlx5 NICs, outstanding descriptors that requested a TX timestamp are completed without a completion entry, and the kernel dereferences that missing entry. The sources describe a NULL pointer dereference in the kernel, which typically means a crash or denial of service rather than code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the running kernel version with `uname -r` and compare it against the fixed kernel release in the NVD entry
- Check whether the mlx5 driver is loaded with `lsmod | grep mlx5_core`
- Check whether AF_XDP sockets are in use on mlx5 interfaces, for example with `ss -xp` or the application's own configuration

## Fix

- Update the Linux kernel to a release that includes the upstream fix for net/mlx5e AF_XDP TX timestamp teardown
- Version numbers are unknown from the sources; check the kernel stable branch referenced in the NVD entry

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98791

## From the sources

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

net/mlx5e: Fix AF_XDP TX timestamp teardown NULL dereference

During XSK TX queue teardown, outstanding descriptors are completed
without a CQE. If one requested a TX timestamp, the completion path
passes that NULL CQE to mlx5e_xsk_fill_timestamp(), which dereferences
it.

Return zero when no CQE is available, indicating that teardown did not
produce a TX timestamp.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_