Linux Kernel up to 6.17.12/6.18.1 Helper Call fpu_vstl uninitialized pointer

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.17.12/6.18.1 and classified as critical. This affects the function fpu_vstl of the component Helper Call Handler. This manipulation causes uninitialized pointer. This vulnerability is tracked as CVE-2025-68751. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.17.12/6.18.1. Affected by this vulnerability is the function fpu_vstl of the component Helper Call Handler. The manipulation with an unknown input leads to a uninitialized pointer vulnerability. The CWE definition for the vulnerability is CWE-824. The product accesses or uses a pointer that has not been initialized. The impact remains unknown. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: s390/fpu: Fix false-positive kmsan report in fpu_vstl() A false-positive kmsan report is detected when running ping command. An inline assembly instruction 'vstl' can write varied amount of bytes depending on value of 'index' argument. If 'index' > 0, 'vstl' writes at least 2 bytes. clang generates kmsan write helper call depending on inline assembly constraints. Constraints are evaluated compile-time, but value of 'index' argument is known only at runtime. clang currently generates call to __msan_instrument_asm_store with 1 byte as size. Manually call kmsan function to indicate correct amount of bytes written and fix false-positive report. This change fixes following kmsan reports: [ 36.563119] ===================================================== [ 36.563594] BUG: KMSAN: uninit-value in virtqueue_add+0x35c6/0x7c70 [ 36.563852] virtqueue_add+0x35c6/0x7c70 [ 36.564016] virtqueue_add_outbuf+0xa0/0xb0 [ 36.564266] start_xmit+0x288c/0x4a20 [ 36.564460] dev_hard_start_xmit+0x302/0x900 [ 36.564649] sch_direct_xmit+0x340/0xea0 [ 36.564894] __dev_queue_xmit+0x2e94/0x59b0 [ 36.565058] neigh_resolve_output+0x936/0xb40 [ 36.565278] __neigh_update+0x2f66/0x3a60 [ 36.565499] neigh_update+0x52/0x60 [ 36.565683] arp_process+0x1588/0x2de0 [ 36.565916] NF_HOOK+0x1da/0x240 [ 36.566087] arp_rcv+0x3e4/0x6e0 [ 36.566306] __netif_receive_skb_list_core+0x1374/0x15a0 [ 36.566527] netif_receive_skb_list_internal+0x1116/0x17d0 [ 36.566710] napi_complete_done+0x376/0x740 [ 36.566918] virtnet_poll+0x1bae/0x2910 [ 36.567130] __napi_poll+0xf4/0x830 [ 36.567294] net_rx_action+0x97c/0x1ed0 [ 36.567556] handle_softirqs+0x306/0xe10 [ 36.567731] irq_exit_rcu+0x14c/0x2e0 [ 36.567910] do_io_irq+0xd4/0x120 [ 36.568139] io_int_handler+0xc2/0xe8 [ 36.568299] arch_cpu_idle+0xb0/0xc0 [ 36.568540] arch_cpu_idle+0x76/0xc0 [ 36.568726] default_idle_call+0x40/0x70 [ 36.568953] do_idle+0x1d6/0x390 [ 36.569486] cpu_startup_entry+0x9a/0xb0 [ 36.569745] rest_init+0x1ea/0x290 [ 36.570029] start_kernel+0x95e/0xb90 [ 36.570348] startup_continue+0x2e/0x40 [ 36.570703] [ 36.570798] Uninit was created at: [ 36.571002] kmem_cache_alloc_node_noprof+0x9e8/0x10e0 [ 36.571261] kmalloc_reserve+0x12a/0x470 [ 36.571553] __alloc_skb+0x310/0x860 [ 36.571844] __ip_append_data+0x483e/0x6a30 [ 36.572170] ip_append_data+0x11c/0x1e0 [ 36.572477] raw_sendmsg+0x1c8c/0x2180 [ 36.572818] inet_sendmsg+0xe6/0x190 [ 36.573142] __sys_sendto+0x55e/0x8e0 [ 36.573392] __s390x_sys_socketcall+0x19ae/0x2ba0 [ 36.573571] __do_syscall+0x12e/0x240 [ 36.573823] system_call+0x6e/0x90 [ 36.573976] [ 36.574017] Byte 35 of 98 is uninitialized [ 36.574082] Memory access of size 98 starts at 0000000007aa0012 [ 36.574218] [ 36.574325] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G B N 6.17.0-dirty #16 NONE [ 36.574541] Tainted: [B]=BAD_PAGE, [N]=TEST [ 36.574617] Hardware name: IBM 3931 A01 703 (KVM/Linux) [ 36.574755] ===================================================== [ 63.532541] ===================================================== [ 63.533639] BUG: KMSAN: uninit-value in virtqueue_add+0x35c6/0x7c70 [ 63.533989] virtqueue_add+0x35c6/0x7c70 [ 63.534940] virtqueue_add_outbuf+0xa0/0xb0 [ 63.535861] start_xmit+0x288c/0x4a20 [ 63.536708] dev_hard_start_xmit+0x302/0x900 [ 63.537020] sch_direct_xmit+0x340/0xea0 [ 63.537997] __dev_queue_xmit+0x2e94/0x59b0 [ 63.538819] neigh_resolve_output+0x936/0xb40 [ 63.539793] ip_finish_output2+0x1ee2/0x2200 [ 63.540784] __ip_finish_output+0x272/0x7a0 [ 63.541765] ip_finish_output+0x4e/0x5e0 [ 63.542791] ip_output+0x166/0x410 [ 63.543771] ip_push_pending_frames+0x1a2/0x470 [ 63.544753] raw_sendmsg+0x1f06/0x2180 [ 63.545033] inet_sendmsg+0xe6/0x190 [ 63.546006] __sys_sendto+0x55e/0x8e0 ---truncated---

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2025-68751 since 12/24/2025. The exploitation appears to be difficult. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 02/13/2026).

The vulnerability scanner Nessus provides a plugin with the ID 281753 (Linux Distros Unpatched Vulnerability : CVE-2025-68751), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.17.13, 6.18.2 or 6.19-rc1 eliminates this vulnerability. Applying the patch 946357a538bb47740635c25520924351d2d91544/13dcd6308cb8f67134ee5d5d762b2a66363c695b/14e4e4175b64dd9216b522f6ece8af6997d063b2 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (281753) and CERT Bund (WID-SEC-2026-0009). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

• Microsoft Azure Linux
• Debian Linux
• Open Source Linux Kernel
• SUSE Linux
• SUSE openSUSE

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.17.0
• 6.17.1
• 6.17.2
• 6.17.3
• 6.17.4
• 6.17.5
• 6.17.6
• 6.17.7
• 6.17.8
• 6.17.9
• 6.17.10
• 6.17.11
• 6.17.12
• 6.18.0
• 6.18.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Exploitinginfo

Threat Intelligenceinfo

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Sourcesinfo

Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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