CVE-2026-43464

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.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Linux Kernel < 6.19.0-rc3

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>

// Conceptual PoC for CVE-2026-43464
// This XDP program triggers the vulnerability by shrinking the tail.
SEC("xdp")
int xdp_shrink_tail(struct xdp_md *ctx) {
    // Shrink the packet size by 256 bytes as mentioned in the description
    // Payload size should be around 3600 bytes to hit the specific frag logic
    int offset = 256;
    int ret = bpf_xdp_adjust_tail(ctx, -offset);
    
    if (ret) {
        return XDP_PASS;
    }
    
    // Return XDP_TX to trigger the frag counting logic in the driver
    return XDP_TX;
}

char _license[] SEC("license") = "GPL";

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-43464
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-43464
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-43464/
[4] VulDB https://vuldb.com/cve/CVE-2026-43464
[5] https://git.kernel.org/stable/c/03cb50e5b74fce8bf6d92b860371b66253cf0f8d
[6] https://git.kernel.org/stable/c/a6413e6f6c9d9bb9833324cb3753582f7bc0f2fa
[7] https://git.kernel.org/stable/c/c74557495efb4bd0adefdfc8678ecdbc82a06da3

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-43464", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-05-08T15:16:59.283", "lastModified": "2026-05-11T08:16:15.477", "vulnStatus": "Received", "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/mlx5e: RX, Fix XDP multi-buf frag counting for legacy RQ\n\nXDP multi-buf programs can modify the layout of the XDP buffer when the\nprogram calls bpf_xdp_pull_data() or bpf_xdp_adjust_tail(). The\nreferenced commit in the fixes tag corrected the assumption in the mlx5\ndriver that the XDP buffer layout doesn't change during a program\nexecution. However, this fix introduced another issue: the dropped\nfragments still need to be counted on the driver side to avoid page\nfragment reference counting issues.\n\nSuch issue can be observed with the\ntest_xdp_native_adjst_tail_shrnk_data selftest when using a payload of\n3600 and shrinking by 256 bytes (an upcoming selftest patch): the last\nfragment gets released by the XDP code but doesn't get tracked by the\ndriver. This results in a negative pp_ref_count during page release and\nthe following splat:\n\n  WARNING: include/net/page_pool/helpers.h:297 at mlx5e_page_release_fragmented.isra.0+0x4a/0x50 [mlx5_core], CPU#12: ip/3137\n  Modules linked in: [...]\n  CPU: 12 UID: 0 PID: 3137 Comm: ip Not tainted 6.19.0-rc3+ #12 NONE\n  Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014\n  RIP: 0010:mlx5e_page_release_fragmented.isra.0+0x4a/0x50 [mlx5_core]\n  [...]\n  Call Trace:\n   <TASK>\n   mlx5e_dealloc_rx_wqe+0xcb/0x1a0 [mlx5_core]\n   mlx5e_free_rx_descs+0x7f/0x110 [mlx5_core]\n   mlx5e_close_rq+0x50/0x60 [mlx5_core]\n   mlx5e_close_queues+0x36/0x2c0 [mlx5_core]\n   mlx5e_close_channel+0x1c/0x50 [mlx5_core]\n   mlx5e_close_channels+0x45/0x80 [mlx5_core]\n   mlx5e_safe_switch_params+0x1a5/0x230 [mlx5_core]\n   mlx5e_change_mtu+0xf3/0x2f0 [mlx5_core]\n   netif_set_mtu_ext+0xf1/0x230\n   do_setlink.isra.0+0x219/0x1180\n   rtnl_newlink+0x79f/0xb60\n   rtnetlink_rcv_msg+0x213/0x3a0\n   netlink_rcv_skb+0x48/0xf0\n   netlink_unicast+0x24a/0x350\n   netlink_sendmsg+0x1ee/0x410\n   __sock_sendmsg+0x38/0x60\n   ____sys_sendmsg+0x232/0x280\n   ___sys_sendmsg+0x78/0xb0\n   __sys_sendmsg+0x5f/0xb0\n   [...]\n   do_syscall_64+0x57/0xc50\n\nThis patch fixes the issue by doing page frag counting on all the\noriginal XDP buffer fragments for all relevant XDP actions (XDP_TX ,\nXDP_REDIRECT and XDP_PASS). This is basically reverting to the original\ncounting before the commit in the fixes tag.\n\nAs frag_page is still pointing to the original tail, the nr_frags\nparameter to xdp_update_skb_frags_info() needs to be calculated\nin a different way to reflect the new nr_frags."}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "references": [{"url": "https://git.kernel.org/stable/c/03cb50e5b74fce8bf6d92b860371b66253cf0f8d", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/a6413e6f6c9d9bb9833324cb3753582f7bc0f2fa", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}, {"url": "https://git.kernel.org/stable/c/c74557495efb4bd0adefdfc8678ecdbc82a06da3", "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}]}}