CVE-2026-90191 (GCVE-0-2026-90191)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:07 – Updated: 2026-10-19 08:59
VLAI
Title
mailbox: riscv-sbi-mpxy: validate RPMI notification lengths
Summary
In the Linux kernel, the following vulnerability has been resolved: mailbox: riscv-sbi-mpxy: validate RPMI notification lengths The SBI return value controls how many bytes are copied from shared memory into the RPMI notification buffer. It is not validated against the negotiated shared-memory size before that copy. The event walker also uses a reversed loop condition and can inspect a short event record. Validate the complete notification length before copying it, iterate only while a full event header remains, and stop when a declared event payload extends beyond the copied notification data.
Severity
8.4 (High)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6639 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: bf3022a4eb119c6b4e3424d6b19d8bfdfbc9bb57 , < cbc24bce70dfd91c7b2f53b4fa896e9a4b6d6a6b (git)
Affected: bf3022a4eb119c6b4e3424d6b19d8bfdfbc9bb57 , < c7bc5e7677bcda7a446d63b989cfaa3fe91d6b76 (git)
Affected: bf3022a4eb119c6b4e3424d6b19d8bfdfbc9bb57 , < 11d5af151bcbe78f5a579e0faecd3be9cea0399a (git)
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Linux Linux Affected: 6.18
Unaffected: 0 , < 6.18 (semver)
Unaffected: 6.18.52 , ≤ 6.18.* (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/mailbox/riscv-sbi-mpxy-mbox.c"
          ],
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              "versionType": "git"
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          "vendor": "Linux",
          "versions": [
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              "version": "6.18"
            },
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              "version": "0",
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              "version": "6.18.52",
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              "version": "7.2.6",
              "versionType": "semver"
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              "versionType": "original_commit_for_fix"
            }
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      ],
      "cpeApplicability": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "versionStartIncluding": "6.18",
                  "vulnerable": true
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                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
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      "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": {
            "baseScore": 8.4,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "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-\u003enotif 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-\u003enotif. KVM\u0027s 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-\u003eshmem, 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-\u003enotif, 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."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:59:27.897Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/c7bc5e7677bcda7a446d63b989cfaa3fe91d6b76"
        },
        {
          "url": "https://git.kernel.org/stable/c/11d5af151bcbe78f5a579e0faecd3be9cea0399a"
        }
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      "title": "mailbox: riscv-sbi-mpxy: validate RPMI notification lengths",
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        "engine": "bippy-1.2.0"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-90191",
    "datePublished": "2026-09-17T16:07:12.339Z",
    "dateReserved": "2026-09-11T19:38:34.792Z",
    "dateUpdated": "2026-10-19T08:59:27.897Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-11-09",
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      "percentile": "0.07427"
    },
    "microsoft_vex": {
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      "id": "msrc_CVE-2026-90191",
      "initial_release_date": "2026-10-20T22:21:52.000Z",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "mailbox: riscv-sbi-mpxy: validate RPMI notification lengths",
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      "version": "2"
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                "product": "Linux",
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                ],
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          {
            "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."
          }
        ],
        "id": "CVE-2026-90191",
        "lastModified": "2026-10-19T09:19:09.117",
        "metrics": {
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      "id": "CVE-2026-90191",
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      "product_status:known_not_affected": "203",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: mailbox: riscv-sbi-mpxy: validate RPMI notification lengths",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-90191.json",
      "version": "3"
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  }
}



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