# CVE-2026-43465: net/mlx5e: RX, Fix XDP multi-buf frag counting for striding RQ > A reference counting error in the mlx5 network driver can cause negative page reference counts, leading to kernel warnings and potential system instability. - **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 8 May 2026 - **Updated:** 21 Oct 2026 - **Also known as:** AZL-87060, BELL-CVE-2026-43465, DEBIAN-CVE-2026-43465, GHSA-wm82-xv2w-22mm, ROOT-OS-DEBIAN-13-CVE-2026-43465, ROOT-OS-UBUNTU-2404-CVE-2026-43465, UBUNTU-CVE-2026-43465 ## What is CVE-2026-43465? CVE-2026-43465 is a critical memory corruption vulnerability in Linux kernel, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description 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: 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. ## Which versions are affected by CVE-2026-43465? It affects 1 product. Products: Linux kernel. ## How do I fix CVE-2026-43465? Apply the vendor's patch. ## Is CVE-2026-43465 being exploited? There is no known exploitation of CVE-2026-43465 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-43465 and fix it if it is affected. What it is: CVE-2026-43465 is a critical memory corruption vulnerability in Linux kernel, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-43465 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-43465/ (Markdown: https://insights.sbomify.com/CVE-2026-43465/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43465 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43465 - OSV: https://osv.dev/vulnerability/CVE-2026-43465 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-43465/ Summaries are generated and may contain mistakes; the official description above is the record.