---
id: "CVE-2026-99079"
kind: "vulnerability"
aliases: ["CVE-2026-99079"]
title: "Linux kernel: mlx5 XSK refill retry can publish the same buffer twice"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["afxdp", "bare-metal", "infrastructure", "linux-kernel", "mlx5", "xdp"]
not_affected_if: ["no-afxdp-zero-copy", "no-mlx5-nic"]
published_at: "2026-10-23T13:17:32+00:00"
first_seen_at: "2026-10-23T21:57:34+00:00"
updated_at: "2026-10-25T04:53:39+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99079", "first_seen_at": "2026-10-23T21:57:34+00:00"}]
---

# Linux kernel: mlx5 XSK refill retry can publish the same buffer twice

In the Linux mlx5e driver, a partially failed refill of an AF_XDP receive ring can leave a stale buffer pointer that is freed again on retry. The sources report that this causes the same UMEM frame to be published twice, which can corrupt packet data.

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

## How to check

- unknown

## Fix

- unknown

## Timeline

- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99079

## From the sources

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

net/mlx5e: Prevent stale XSK buffer release on refill retry

When an XDP redirect to an AF_XDP socket fails because its RX ring is
full, the XSK core frees the buffer. During the subsequent batched refill
of a legacy cyclic RQ, mlx5e also releases the WQE's XSK buffer before
allocating a replacement. If that refill succeeds only partially, a WQE
left without a replacement retains its old buffer pointer.

The buffer can meanwhile be allocated to another WQE. A later refill
retry can then free the live buffer through the stale pointer and publish
the same UMEM frame twice.

Mark the WQE as released immediately after the driver-side free. The flag
is already cleared when a replacement buffer is assigned, so refill
retries no longer release stale pointers.

The failure is silent and produces no kernel warning or splat. A
standalone legacy cyclic-RQ zero-copy libxsk reproducer, using 64-byte UDP
traffic offered at 12 Mpps, detected it: stock stopped after 2,854,914
packets in 4.094 seconds, with 4,542 xdp_rx_ring_full events and 64
ownership/double-publication errors. With this change it processed
356,904,225 packets in 30 seconds despite 571,405 xdp_rx_ring_full events,
with no ownership or data errors.

---

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