CVE-2026-89483

Received Received - Intake

Uninitialized Memory Exposure in Linux Kernel NVMe

Publication date: 2026-09-11

Last updated on: 2026-09-14

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: nvme: zero the discard fallback page nvme_setup_discard() always maps sizeof(struct nvme_dsm_range) * NVME_DSM_MAX_RANGES = 4096 bytes as the DSM payload however many ranges the command declares, because some devices ignore the 'Number of Ranges' field - the Fixes: commit records two that read past the declared ranges. A single-range discard fills only the first 16 bytes. Normally the buffer comes from kzalloc() and the other 4080 bytes are zero. When that allocation fails the code falls back to the per-controller ctrl->discard_page, which nvme_init_ctrl() obtains with alloc_page(GFP_KERNEL) and nothing ever zeroes, so those 4080 bytes are whatever the page last held and are handed to the controller. Reaching it requires the kzalloc(GFP_ATOMIC | __GFP_NOWARN) to fail, that is memory pressure; it is not remotely triggerable. Failing the allocation under KMSAN reproduces it, with the leaked tail full of vmemmap struct page pointers. The extent in the report is a partial transfer of the payload, not the whole 4096 bytes; the 16-byte boundary in it is the one declared range: [ 11.991601] BUG: KMSAN: uninit-value in dma_map_phys+0x14c8/0x1900 [ 11.991969] dma_map_phys+0x14c8/0x1900 [ 11.992220] dma_map_page_attrs+0xcf/0x130 [ 11.992485] e1000_xmit_frame+0x4099/0x6d10 [ 11.992768] dev_hard_start_xmit+0x22f/0xa80 [ 11.993068] sch_direct_xmit+0x35c/0xcb0 [ 11.993315] __dev_queue_xmit+0x1ee5/0x5eb0 [ 11.993608] ip_finish_output2+0x1903/0x1c30 [ 11.993881] ip_finish_output+0x288/0x870 [ 11.994125] ip_output+0x15e/0x400 [ 11.994365] __ip_queue_xmit+0x1e85/0x1fb0 [ 11.994639] ip_queue_xmit+0x60/0x80 [ 11.994899] __tcp_transmit_skb+0x4e71/0x5fa0 [ 11.995210] tcp_write_xmit+0x3a36/0x9160 [ 11.995533] __tcp_push_pending_frames+0xc5/0x3c0 [ 11.995854] tcp_push+0x7dc/0x840 [ 11.996076] tcp_sendmsg_locked+0x766c/0x8400 [ 11.996371] tcp_sendmsg+0x4b/0x90 [ 11.996572] inet_sendmsg+0x134/0x2a0 [ 11.996823] __sock_sendmsg+0x265/0x360 [ 11.997076] sock_sendmsg+0x100/0x1e0 [ 11.997293] nvme_tcp_try_send+0x196f/0x6370 [ 11.997605] nvme_tcp_queue_rq+0x1d54/0x20b0 [ 11.997882] blk_mq_dispatch_rq_list+0x5ee/0x2e50 [ 11.998175] __blk_mq_sched_dispatch_requests+0x16dc/0x24a0 [ 11.998539] blk_mq_sched_dispatch_requests+0x11b/0x2c0 [ 11.998865] blk_mq_run_work_fn+0x13b/0x280 [ 11.999146] process_scheduled_works+0x966/0x1ad0 [ 11.999465] worker_thread+0xe44/0x1480 [ 11.999709] kthread+0x53b/0x600 [ 11.999927] ret_from_fork+0x29f/0x7c0 [ 12.000191] ret_from_fork_asm+0x1a/0x30 [ 12.000460] [ 12.000558] Uninit was created at: [ 12.000788] __alloc_frozen_pages_noprof+0x8bf/0xd30 [ 12.001096] alloc_pages_mpol+0x1d0/0x5f0 [ 12.001326] alloc_pages_noprof+0x102/0x290 [ 12.001627] nvme_init_ctrl+0x5a3/0x9f0 [ 12.001891] nvme_tcp_create_ctrl+0xd75/0x19b0 [ 12.002170] nvmf_dev_write+0x4c68/0x4fd0 [ 12.002426] vfs_write+0x587/0x1a10 [ 12.002636] __x64_sys_write+0x207/0x4f0 [ 12.002874] x64_sys_call+0x2ff0/0x3ea0 [ 12.003123] do_syscall_64+0x147/0x3b0 [ 12.003400] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 12.003680] [ 12.003777] Bytes 16-2843 of 2844 are uninitialized [ 12.004068] Memory access of size 2844 starts at ffff888109f82000 [ 12.004412] [ 12.004530] CPU: 0 UID: 0 PID: 101 Comm: kworker/0:1H Not tainted 7.2.0-rc5-NVMECTL-gf5098b6bae76 #1 PREEMPT(lazy) [ 12.005127] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 12.005762] Workqueue: kblockd blk_mq_run_work_fn [ 12.006073] ===================================================== Allocate the page with __GFP_ZERO. The single allocation site covers every use of it: bytes no discard has written stay zero, and bytes one did write hold that controller's own range list, which it has already been sent.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-11

Last Modified

2026-09-14

Generated

2026-10-02

AI Q&A

2026-09-12

EPSS Evaluated

2026-09-29

NVD

CVE-2026-89483

EUVD

EUVD-2026-76389

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a potential information leak during NVMe discard operations. When memory allocation fails, the code falls back to an uninitialized page that may contain sensitive data like vmemmap struct page pointers. The issue occurs because the fallback page is not zeroed before use, leading to uninitialized memory being sent to the controller.

Detection Guidance

This vulnerability is specific to the Linux kernel's NVMe driver and requires kernel memory sanitizer (KMSAN) to detect uninitialized memory exposure. No standard network or system commands can directly detect it. The issue manifests under memory pressure when kzalloc fails and falls back to an uninitialized page. Use KMSAN-enabled kernels for detection.

Impact Analysis

This vulnerability could expose sensitive kernel memory contents to unprivileged users or attackers. While exploitation requires memory pressure conditions and is not remotely triggerable, it may allow disclosure of internal kernel structures or other sensitive data in certain scenarios.

Compliance Impact

This vulnerability involves uninitialized memory being exposed in discard operations, which could potentially leak sensitive data. While not directly tied to GDPR or HIPAA, such memory leaks could violate data protection principles by exposing residual data during storage operations. However, the provided context does not explicitly link this issue to compliance requirements.

Mitigation Strategies

Apply the kernel patch that allocates the discard fallback page with __GFP_ZERO. Update to a fixed kernel version where this issue is resolved. Monitor memory pressure conditions as the vulnerability is only triggerable under such scenarios.

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