{"id":"CVE-2026-99155","state":"PUBLISHED","title":"scsi: xen/scsifront: Check for a NULL shadow entry on a backend response","description":"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->shadow[], but then\ndereferences the entry to test ->inflight 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.","publishedAt":"2026-10-28T10:35:09.733Z","updatedAt":"2026-10-30T12:42:21.472Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"448b9a8b530b753d346dab10add09a502fc719a4","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"e397d4da76bed72db6ac4a0848fb6217f8394dca","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"90186a2354821329a27d92b266c0f05e8f4f637c","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"1d91ec793d6c80eca963d426e0da832d40a062df","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"15791e57f57f7050014d08cfe239d4aa1e6b94b0","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"8c8222c255772713eb36cde695777a1fce224917","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/scsi/xen-scsifront.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.161","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.115","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.59","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.13","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/scsi/xen-scsifront.c"]}],"references":["https://git.kernel.org/stable/c/448b9a8b530b753d346dab10add09a502fc719a4","https://git.kernel.org/stable/c/e397d4da76bed72db6ac4a0848fb6217f8394dca","https://git.kernel.org/stable/c/90186a2354821329a27d92b266c0f05e8f4f637c","https://git.kernel.org/stable/c/1d91ec793d6c80eca963d426e0da832d40a062df","https://git.kernel.org/stable/c/15791e57f57f7050014d08cfe239d4aa1e6b94b0","https://git.kernel.org/stable/c/8c8222c255772713eb36cde695777a1fce224917"],"weaknesses":[],"ingestedAt":"2026-10-30T13:02:04.640Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/99xxx/CVE-2026-99155.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99155","state":"PUBLISHED","datePublished":"2026-10-28T10:35:09.733Z","dateUpdated":"2026-10-30T12:42:21.472Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.397Z"},"containers":{"cna":{"title":"scsi: xen/scsifront: Check for a NULL shadow entry on a backend response","descriptions":[{"lang":"en","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->shadow[], but then\ndereferences the entry to test ->inflight 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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"448b9a8b530b753d346dab10add09a502fc719a4","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"e397d4da76bed72db6ac4a0848fb6217f8394dca","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"90186a2354821329a27d92b266c0f05e8f4f637c","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"1d91ec793d6c80eca963d426e0da832d40a062df","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"15791e57f57f7050014d08cfe239d4aa1e6b94b0","versionType":"git"},{"version":"6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43","status":"affected","lessThan":"8c8222c255772713eb36cde695777a1fce224917","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/scsi/xen-scsifront.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.19","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.161","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.115","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.59","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.13","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/scsi/xen-scsifront.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/448b9a8b530b753d346dab10add09a502fc719a4"},{"url":"https://git.kernel.org/stable/c/e397d4da76bed72db6ac4a0848fb6217f8394dca"},{"url":"https://git.kernel.org/stable/c/90186a2354821329a27d92b266c0f05e8f4f637c"},{"url":"https://git.kernel.org/stable/c/1d91ec793d6c80eca963d426e0da832d40a062df"},{"url":"https://git.kernel.org/stable/c/15791e57f57f7050014d08cfe239d4aa1e6b94b0"},{"url":"https://git.kernel.org/stable/c/8c8222c255772713eb36cde695777a1fce224917"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:42:21.472Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.6.161"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.12.115"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"6.18.59"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"7.2.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.19","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}