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Fencer Vulns
critical 9.8

CVE-2026-43465 in the critical feed json

net/mlx5e: RX, Fix XDP multi-buf frag counting for striding RQ

published 2026-05-08 6 mo ago modified 2026-10-21 19 d ago also EUVD-2026-28771

cvss
9.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits
0
none known

Summary

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

net/mlx5e: RX, Fix XDP multi-buf frag counting for striding 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.

The issue was discovered by the drivers/net/xdp.py selftest, more specifically the test_xdp_native_tx_mb: - The mlx5 driver allocates a page_pool page and initializes it with a frag counter of 64 (pp_ref_count=64) and the internal frag counter to 0. - The test sends one packet with no payload. - On RX (mlx5e_skb_from_cqe_mpwrq_nonlinear()), mlx5 configures the XDP buffer with the packet data starting in the first fragment which is the page mentioned above. - The XDP program runs and calls bpf_xdp_pull_data() which moves the header into the linear part of the XDP buffer. As the packet doesn't contain more data, the program drops the tail fragment since it no longer contains any payload (pp_ref_count=63). - mlx5 device skips counting this fragment. Internal frag counter remains 0. - mlx5 releases all 64 fragments of the page but page pp_ref_count is 63 => negative reference counting error.

Resulting splat during the test:

WARNING: CPU: 0 PID: 188225 at ./include/net/page_pool/helpers.h:297 mlx5e_page_release_fragmented.isra.0+0xbd/0xe0 [mlx5_core] Modules linked in: [...] CPU: 0 UID: 0 PID: 188225 Comm: ip Not tainted 6.18.0-rc7_for_upstream_min_debug_2025_12_08_11_44 #1 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014 RIP: 0010:mlx5e_page_release_fragmented.isra.0+0xbd/0xe0 [mlx5_core] [...] Call Trace: <TASK> mlx5e_free_rx_mpwqe+0x20a/0x250 [mlx5_core] mlx5e_dealloc_rx_mpwqe+0x37/0xb0 [mlx5_core] mlx5e_free_rx_descs+0x11a/0x170 [mlx5_core] mlx5e_close_rq+0x78/0xa0 [mlx5_core] mlx5e_close_queues+0x46/0x2a0 [mlx5_core] mlx5e_close_channel+0x24/0x90 [mlx5_core] mlx5e_close_channels+0x5d/0xf0 [mlx5_core] mlx5e_safe_switch_params+0x2ec/0x380 [mlx5_core] mlx5e_change_mtu+0x11d/0x490 [mlx5_core] mlx5e_change_nic_mtu+0x19/0x30 [mlx5_core] netif_set_mtu_ext+0xfc/0x240 do_setlink.isra.0+0x226/0x1100 rtnl_newlink+0x7a9/0xba0 rtnetlink_rcv_msg+0x220/0x3c0 netlink_rcv_skb+0x4b/0xf0 netlink_unicast+0x255/0x380 netlink_sendmsg+0x1f3/0x420 __sock_sendmsg+0x38/0x60 ____sys_sendmsg+0x1e8/0x240 ___sys_sendmsg+0x7c/0xb0 [...] __sys_sendmsg+0x5f/0xb0 do_syscall_64+0x55/0xc70

The problem applies for XDP_PASS as well which is handled in a different code path in the driver.

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.

Patch / fix

  • Linux Linux 6.6.160, 6.12.114, 6.18, 6.18.19, 6.19.9, 7.0
  • linux Debian 13 6.12.115-2
  • linux Debian 14 6.19.10-1

debian advisories DEBIAN-CVE-2026-43465

  • linux Ubuntu 24.04 LTS 6.8.0-137.137
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1062.65
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1065.73
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1060.68
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1062.63
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1064.72
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1047.51
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1062.66

ubuntu advisories UBUNTU-CVE-2026-43465

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-50.2
  • kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-50.1
  • kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-50.1
  • kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-50.1
  • kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-50.2
  • kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.73.2
  • kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.73.1
  • kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.53.73.2

suse advisories SUSE-SU-2026:22810-1SUSE-SU-2026:22809-1SUSE-SU-2026:22904-1SUSE-SU-2026:22903-1SUSE-SU-2026:3166-1SUSE-SU-2026:22742-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.36.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.36.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.36.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.36.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.36.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.36.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.36.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.36.1

opensuse advisories openSUSE-SU-2026:21388-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-43465 updated cvss 5.5

kernel: net/mlx5e: RX, Fix XDP multi-buf frag counting for striding RQ

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “To mitigate this issue, prevent the mlx5_core module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.”
  • Red Hat Enterprise Linux 10 kernel
    affected: workaround, no fix available “To mitigate this issue, prevent the mlx5_core module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.54% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Technology feeds

References

Sources

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