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Linux KernelOperating system · Linux

CVE-2026-43465

CRITICAL · 9.8 CVSS v3.1 Published 2026-05-08
Fix available
A fix is available. Upgrade to 6.7 / 6.13 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A vulnerability in the Linux kernel's mlx5e driver causes incorrect fragment counting when XDP multi-buffer programs modify the XDP buffer layout via bpf_xdp_pull_data() or bpf_xdp_adjust_tail(). When fragments are dropped by the XDP program, the driver fails to count them, leading to negative page reference counting errors (page ref count becomes 63 instead of 0), causing kernel warnings and potential memory corruption.

MitigationApply the kernel patch that restores proper fragment counting for all original XDP buffer fragments across XDP_TX, XDP_REDIRECT, and XDP_PASS actions. As a workaround, avoid using XDP multi-buffer programs that call bpf_xdp_pull_data() or bpf_xdp_adjust_tail() on affected kernels.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 6.6.115, < 6.7>= 6.12.56, < 6.13>= 6.17.6, < 6.18>= 6.18.1, < 6.18.19>= 6.19, < 6.19.9= 6.18= 7.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify kernel version
    Run 'uname -r' to get the running kernel version
    Affected if The version falls within any of these ranges: >= 6.6.115 and < 6.7, >= 6.12.56 and < 6.13, >= 6.17.6 and < 6.18, >= 6.18.1 and < 6.18.19, >= 6.19 and < 6.19.9, equals 6.18, or equals 7.0
  2. Verify mlx5e driver is loaded
    Run 'lsmod | grep mlx5' or check 'ethtool -i <interface>' for a Mellanox network interface
    Affected if The mlx5e driver is loaded and active for a network interface
  3. Confirm XDP multi-buffer program usage
    Check for loaded XDP programs using 'ip link show' or 'bpftool net' and verify if they process multiple packet buffers
    Affected if An XDP program is attached that handles multi-buffer packets (large packets split across multiple buffers)
  4. Identify if bpf_xdp_pull_data or bpf_xdp_adjust_tail is used
    Inspect the XDP program binary using 'bpftool prog dump' or review source code for calls to bpf_xdp_pull_data() or bpf_xdp_adjust_tail()
    Affected if The XDP program calls either bpf_xdp_pull_data() or bpf_xdp_adjust_tail() to modify buffer layout
  5. Check for page ref count kernel warnings
    Review kernel logs with 'dmesg' or 'journalctl -k' for messages containing 'page: refcount' or 'page ref count'
    Affected if Kernel warnings show page reference count errors (such as count becoming 63 instead of 0) on network packet handling

You are affected if you run a listed kernel version with an active mlx5e driver and use XDP multi-buffer programs that call bpf_xdp_pull_data() or bpf_xdp_adjust_tail(), especially if page ref count warnings appear in kernel logs.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.7 / 6.13 / 6.18 or later
Fixed in 6.76.136.18
Vendor patch git.kernel.org →
Interim mitigation

Apply the kernel patch that restores proper fragment counting for all original XDP buffer fragments across XDP_TX, XDP_REDIRECT, and XDP_PASS actions. As a workaround, avoid using XDP multi-buffer programs that call bpf_xdp_pull_data() or bpf_xdp_adjust_tail() on affected kernels.

Recommended fix High confidence

Kernel 6.18.19 or later (or 6.13+, 6.18+, depending on which branch is in use)

  1. Identify the current running kernel version using `uname -r`
  2. Check if the current version falls within any affected range: >= 6.6.115 and < 6.7, >= 6.12.56 and < 6.13, >= 6.17.6 and < 6.18, or >= 6.18.1 and < 6.18.19
  3. If affected, upgrade to a fixed kernel version: 6.7 or later for the 6.6 branch, 6.13 or later for the 6.12 branch, 6.18.19 or later for the 6.18 branch, or 6.18.19 or later for the 6.17 branch
  4. After upgrade, reboot the system to load the fixed kernel
  5. Verify the fix is applied by checking the kernel version and confirming the mlx5 driver loads without errors
Caveat Kernel upgrades may require rebuild of out-of-tree modules; ensure mlx5 driver modules are compatible with the new kernel version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-43465 in production — separate from our analysis above.

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