CVE-2026-89515

Received Received - Intake

Uninit Value in Linux Kernel SCSI Core

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: scsi: core: Fill in DMA padding bytes in scsi_alloc_sgtables() During fuzz testing, the following issue was discovered: BUG: KMSAN: uninit-value in __dma_map_sg_attrs+0x217/0x310 __dma_map_sg_attrs+0x217/0x310 dma_map_sg_attrs+0x4a/0x70 ata_qc_issue+0x9f8/0x1420 __ata_scsi_queuecmd+0x1657/0x1740 ata_scsi_queuecmd+0x79a/0x920 scsi_queue_rq+0x4472/0x4f40 blk_mq_dispatch_rq_list+0x1cca/0x3ee0 __blk_mq_sched_dispatch_requests+0x458/0x630 blk_mq_sched_dispatch_requests+0x15b/0x340 __blk_mq_run_hw_queue+0xe5/0x250 __blk_mq_delay_run_hw_queue+0x138/0x780 blk_mq_run_hw_queue+0x4bb/0x7e0 blk_mq_sched_insert_request+0x2a7/0x4c0 blk_execute_rq+0x497/0x8a0 sg_io+0xbe0/0xe20 scsi_ioctl+0x2b36/0x3c60 sr_block_ioctl+0x319/0x440 blkdev_ioctl+0x80f/0xd70 __se_sys_ioctl+0x219/0x420 __x64_sys_ioctl+0x93/0xe0 x64_sys_call+0x1d6c/0x3ad0 do_syscall_64+0x4c/0xa0 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Uninit was created at: __alloc_pages+0x5c0/0xc80 alloc_pages+0xe0e/0x1050 blk_rq_map_user_iov+0x2b77/0x6100 blk_rq_map_user_io+0x2fa/0x4d0 sg_io+0xad6/0xe20 scsi_ioctl+0x2b36/0x3c60 sr_block_ioctl+0x319/0x440 blkdev_ioctl+0x80f/0xd70 __se_sys_ioctl+0x219/0x420 __x64_sys_ioctl+0x93/0xe0 x64_sys_call+0x1d6c/0x3ad0 do_syscall_64+0x4c/0xa0 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Bytes 14-15 of 16 are uninitialized Memory access of size 16 starts at ffff88800cbdb000 When processing the last unaligned element of the scatterlist, it is supplemented with missing bytes in the amount of pad_len. These bytes remain uninitialized, which leads to a problem. Extend last_sg->length by pad_len first, then use sg_zero_buffer() to zero those pad_len bytes. sg_zero_buffer() uses sg_miter internally, which correctly handles sg entries spanning multiple pages and padding that crosses a page boundary. Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-09-11

Last Modified

2026-09-11

Generated

2026-09-12

AI Q&A

2026-09-12

EPSS Evaluated

N/A

NVD

CVE-2026-89515

EUVD

EUVD-2026-76421

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 is a Linux kernel vulnerability where uninitialized memory is used during DMA operations. When processing the last unaligned element of a scatterlist, padding bytes are added but remain uninitialized. This can lead to information leaks or memory corruption when the DMA mapping is performed.

Detection Guidance

This vulnerability is specific to the Linux kernel's SCSI subsystem and requires kernel-level detection. It was found during fuzz testing with Syzkaller, so manual detection would involve running kernel fuzzers or checking for uninitialized memory access in SCSI-related operations. No direct network or system commands are provided in the context to detect this issue.

Impact Analysis

This vulnerability could allow attackers to read uninitialized memory during DMA operations, potentially exposing sensitive data. It may also cause system instability or crashes if the uninitialized memory affects critical operations.

Mitigation Strategies

Apply the Linux kernel patch that resolves this issue. The vulnerability is fixed by properly initializing DMA padding bytes in scsi_alloc_sgtables(). Update to a kernel version that includes this fix or backport the patch to your current kernel version.

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