{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-90191", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.792Z", "datePublished": "2026-09-17T16:07:12.339Z", "dateUpdated": "2026-10-19T08:59:27.897Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:59:27.897Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmailbox: riscv-sbi-mpxy: validate RPMI notification lengths\n\nThe SBI return value controls how many bytes are copied from shared\nmemory into the RPMI notification buffer. It is not validated against\nthe negotiated shared-memory size before that copy. The event walker\nalso uses a reversed loop condition and can inspect a short event record.\n\nValidate the complete notification length before copying it, iterate only\nwhile a full event header remains, and stop when a declared event payload\nextends beyond the copied notification data." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.4, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The malformed length is sret.value from sbi_ecall(SBI_EXT_MPXY, SBI_EXT_MPXY_GET_NOTIFICATION_EVENTS) in mpxy_get_notifications(), invoked by mpxy_mbox_irq_thread via mpxy_mbox_peek_data when the MPXY channel MSI fires. That SBI shared-memory/return path is on-chip firmware or an RPMI platform MCU, not a network, Bluetooth, or USB protocol.\nAC:L - A malicious SBI MPXY implementation fully controls sret.value. Returning a length greater than mpxy_shmem_size-sizeof(*notif_data), or a negative value so that sret.value+16 wraps to size_t, makes memcpy() overflow the mpxy_shmem_size mchan->notif buffer on every successful GET_NOTIFICATION_EVENTS with no race.\nPR:N - mpxy_mbox_irq_thread has no capable() or credential check. After rpmi_clk_probe()/rpmi_sysmsi_probe() call mbox_request_channel(), mpxy_mbox_startup() enables the MSI via request_threaded_irq(); compromised SBI firmware or the RPMI microcontroller can fire that IRQ and return the bad length without a Linux user account.\nUI:N - mpxy_mbox_startup() enables MSI and events when clk-rpmi or rpmi-sysmsi bind at boot via mbox_request_channel(). The firmware then delivers GET_NOTIFICATION_EVENTS through mpxy_mbox_irq_thread; no victim must open a device, mount a filesystem, or otherwise interact.\nS:U - memcpy() corrupts host kernel heap around mchan->notif. KVM's vcpu_sbi_ext_mpxy only forwards guest SBI MPXY ECALLs to userspace (and is default_disabled) and never enters this mailbox driver, so this is not a guest-to-host escape.\nC:H - memcpy(notif_data, mpxy->shmem, sret.value+16) over-reads past the per-CPU shmem pages and writes firmware-controlled bytes past the mpxy_shmem_size kmalloc notif buffer, a heap overflow that can be leveraged for kernel memory disclosure.\nI:H - The same unbounded memcpy is a heap out-of-bounds write of SBI-controlled shared-memory contents past mchan->notif, smashing adjacent slab objects and enabling control-flow hijacking.\nA:H - Copying a huge or wrapped sret.value into the mpxy_shmem_size notif allocation walks unmapped heap/guard pages or corrupts allocator metadata, causing a kernel oops or panic in mpxy_mbox_irq_thread." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/mailbox/riscv-sbi-mpxy-mbox.c" ], "versions": [ { "version": "bf3022a4eb119c6b4e3424d6b19d8bfdfbc9bb57", "lessThan": "cbc24bce70dfd91c7b2f53b4fa896e9a4b6d6a6b", "status": "affected", "versionType": "git" }, { "version": "bf3022a4eb119c6b4e3424d6b19d8bfdfbc9bb57", "lessThan": "c7bc5e7677bcda7a446d63b989cfaa3fe91d6b76", "status": "affected", "versionType": "git" }, { "version": "bf3022a4eb119c6b4e3424d6b19d8bfdfbc9bb57", "lessThan": "11d5af151bcbe78f5a579e0faecd3be9cea0399a", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/mailbox/riscv-sbi-mpxy-mbox.c" ], "versions": [ { "version": "6.18", "status": "affected" }, { "version": "0", "lessThan": "6.18", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.52", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.6", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "6.18.52" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "7.2.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/cbc24bce70dfd91c7b2f53b4fa896e9a4b6d6a6b" }, { "url": "https://git.kernel.org/stable/c/c7bc5e7677bcda7a446d63b989cfaa3fe91d6b76" }, { "url": "https://git.kernel.org/stable/c/11d5af151bcbe78f5a579e0faecd3be9cea0399a" } ], "title": "mailbox: riscv-sbi-mpxy: validate RPMI notification lengths", "x_generator": { "engine": "bippy-1.2.0" } } } }