CVE-2026-99155 (GCVE-0-2026-99155)

Vulnerability from cvelistv5 – Published: 2026-10-28 10:35 – Updated: 2026-10-30 12:42
VLAI
Title
scsi: xen/scsifront: Check for a NULL shadow entry on a backend response
Summary
In the Linux kernel, the following vulnerability has been resolved: scsi: xen/scsifront: Check for a NULL shadow entry on a backend response scsifront_do_response() validates the rqid in a backend response against VSCSIIF_MAX_REQS before using it to index info->shadow[], but then dereferences the entry to test ->inflight without checking that the slot is populated. Shadow slots are NULL before a command is submitted (the host private area is zeroed at allocation) and are reset to NULL in _scsifront_put_rqid() once a request completes, so an in-range rqid that does not correspond to an outstanding request makes the frontend dereference a NULL pointer. A malicious or buggy backend can thus crash the guest by returning a response whose rqid is in range but not in flight -- for example a spurious response before any command has been issued, or a duplicate of one already completed. The ring has only VSCSIIF_MAX_REQS (16) slots, so before the first command every in-range rqid selects a NULL slot. Reject a response whose shadow slot is not populated.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6846 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 , < 448b9a8b530b753d346dab10add09a502fc719a4 (git)
Affected: 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 , < e397d4da76bed72db6ac4a0848fb6217f8394dca (git)
Affected: 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 , < 90186a2354821329a27d92b266c0f05e8f4f637c (git)
Affected: 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 , < 1d91ec793d6c80eca963d426e0da832d40a062df (git)
Affected: 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 , < 15791e57f57f7050014d08cfe239d4aa1e6b94b0 (git)
Affected: 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 , < 8c8222c255772713eb36cde695777a1fce224917 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.19
Unaffected: 0 , < 5.19 (semver)
Unaffected: 6.1.191 , ≤ 6.1.* (semver)
Unaffected: 6.6.161 , ≤ 6.6.* (semver)
Unaffected: 6.12.115 , ≤ 6.12.* (semver)
Unaffected: 6.18.59 , ≤ 6.18.* (semver)
Unaffected: 7.2.13 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nscsi: xen/scsifront: Check for a NULL shadow entry on a backend response\n\nscsifront_do_response() validates the rqid in a backend response against\nVSCSIIF_MAX_REQS before using it to index info-\u003eshadow[], but then\ndereferences the entry to test -\u003einflight without checking that the slot\nis populated.  Shadow slots are NULL before a command is submitted (the\nhost private area is zeroed at allocation) and are reset to NULL in\n_scsifront_put_rqid() once a request completes, so an in-range rqid that\ndoes not correspond to an outstanding request makes the frontend\ndereference a NULL pointer.\n\nA malicious or buggy backend can thus crash the guest by returning a\nresponse whose rqid is in range but not in flight -- for example a\nspurious response before any command has been issued, or a duplicate of\none already completed.  The ring has only VSCSIIF_MAX_REQS (16) slots,\nso before the first command every in-range rqid selects a NULL slot.\n\nReject a response whose shadow slot is not populated."
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        "lastModified": "2026-10-30T13:21:49.287",
        "metrics": {},
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      "cve": "CVE-2026-99155",
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      "title": "kernel: kernel: xen-scsifront: Denial of Service via NULL pointer dereference",
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      "version": "3"
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  }
}



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