EUVD-2026-64389
GHSA-r9hq-6x72-7q3j
Severity by source
AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Local vhost-scsi ioctl access requires low-privileged host access; scope change reflects host kernel panic triggered via guest I/O path; C:H/I:H retained as theoretical upper bound for kernel compromise beyond DoS.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
vhost-scsi: reject feature changes after endpoint
vhost_scsi_setup_vq_cmds() runs from VHOST_SCSI_SET_ENDPOINT and allocates each command's protection scatterlist array (prot_sgl) according to the acknowledged VIRTIO_SCSI_F_T10_PI bit. The command pools are not rebuilt when VHOST_SET_FEATURES changes that bit later.
Although virtio feature bits must not change after feature negotiation, vhost_scsi_set_features() currently accepts such a request after the endpoint is active and updates acked_features. Enabling T10-PI after endpoint setup therefore leaves prot_sgl NULL while the I/O path follows the new feature bit.
For a 129-page protection payload, vhost_scsi_mapal() passes the missing first chunk to sg_alloc_table_chained():
sg_alloc_table_chained(table, 129, first_chunk=NULL, nents_first_chunk=inline_sg_cnt)
sg_pool_index() then hits:
BUG_ON(nents > SG_CHUNK_SIZE); /* 129 > 128 */
The kernel reported the following call trace and register state:
Call Trace: <TASK> ? __sg_alloc_table+0x1d8/0x250 ? __pfx_vhost_run_work_list+0x10/0x10 [vhost] sg_alloc_table_chained+0x59/0xf0 ? __pfx_sg_pool_alloc+0x10/0x10 ? vhost_scsi_calc_sgls.constprop.0+0x43/0x60 [vhost_scsi] vhost_scsi_handle_vq+0xf02/0x1700 [vhost_scsi] ? __pfx_vhost_scsi_handle_vq+0x10/0x10 [vhost_scsi] vhost_scsi_handle_kick+0x37/0x50 [vhost_scsi] vhost_run_work_list+0x8e/0xd0 [vhost] vhost_task_fn+0xe1/0x210 ret_from_fork+0x348/0x540 </TASK>
RIP: 0010:0x4 CR2 = 0x4 RSP: 0018:ffffc90000dbf940 EFLAGS: 00010202 RAX: ffffffff82396810 RBX: ffff88811dc28b80 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000820 RDI: 0000000000000081
VHOST_F_LOG_ALL is a vhost-specific runtime feature and remains the only exception.
Reject changes to any feature other than VHOST_F_LOG_ALL while the endpoint is active. This preserves the existing runtime log toggle while preventing feature-dependent command resources and data-path state from becoming inconsistent. Userspace must clear the endpoint before changing any other negotiated feature and set the endpoint up again afterward.
AnalysisAI
The vhost-scsi subsystem in the Linux kernel allows a local attacker with low privileges on a KVM virtualization host to trigger a kernel BUG_ON assertion and crash the host by manipulating VIRTIO feature bits after SCSI endpoint setup. The flaw is that vhost_scsi_set_features() incorrectly accepted changes to VIRTIO_SCSI_F_T10_PI after an active endpoint was established, leaving per-command protection scatterlist arrays (prot_sgl) unallocated while the I/O path proceeded under the updated feature state; when a 129-page protection payload arrives, a BUG_ON(nents > SG_CHUNK_SIZE) fires in sg_pool_index(), panicking the host kernel. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local access to a Linux KVM hypervisor host with the vhost-scsi module loaded and an active SCSI endpoint established via VHOST_SCSI_SET_ENDPOINT. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Despite the CVSS 8.8 score with a Scope Changed vector, real-world exploitation risk is considerably lower than the raw number implies. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local attacker with low-privileged host access to a KVM system running QEMU with a vhost-scsi backend first calls VHOST_SCSI_SET_ENDPOINT to activate the endpoint - causing prot_sgl to be allocated based on the current (T10-PI off) feature state - then issues VHOST_SET_FEATURES to enable VIRTIO_SCSI_F_T10_PI on the live endpoint without triggering command pool reallocation. The attacker, or a guest VM under their control, then submits a SCSI write command carrying 129 pages of T10 protection information, causing vhost_scsi_mapal() to pass NULL as first_chunk to sg_alloc_table_chained(), triggering BUG_ON in sg_pool_index() and crashing the host kernel. … |
| Remediation | Upgrade to a patched Linux kernel: version 6.18.45, 7.1.9, or 7.2 (mainline), per the three confirmed stable backport commits at https://git.kernel.org/stable/c/a06e4611d45518896fbff4f45d9581578b107e91, https://git.kernel.org/stable/c/9a3eb77a612f9d158e4d27df43677a014e9cfa55, and https://git.kernel.org/stable/c/42bc45df5905e2b7dccb72adaf7730f66cfbe03f. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all KVM host systems running Linux kernel versions prior to 6.18.45, 7.1.9, or 7.2 mainline. …
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