{"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":"2026-09-18T17:53:38.782Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-18T17:53:38.782Z"},"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-rc1","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-rc1"}]}]}],"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"}}}}