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

Vulnerability from cvelistv5 – Published: 2026-09-17 16:07 – Updated: 2026-09-18 17:53
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
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-rc1 , ≤ * (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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              "negate": false,
              "operator": "OR"
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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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
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            "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": "2026-09-18T17:53:38.782Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/cbc24bce70dfd91c7b2f53b4fa896e9a4b6d6a6b"
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          "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",
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    "cveId": "CVE-2026-90191",
    "datePublished": "2026-09-17T16:07:12.339Z",
    "dateReserved": "2026-09-11T19:38:34.792Z",
    "dateUpdated": "2026-09-18T17:53:38.782Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-09-25",
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                "product": "Linux",
                "programFiles": [
                  "drivers/mailbox/riscv-sbi-mpxy-mbox.c"
                ],
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                    "status": "unaffected",
                    "version": "7.2.6",
                    "versionType": "semver"
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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."
          }
        ],
        "id": "CVE-2026-90191",
        "lastModified": "2026-09-18T18:17:45.823",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 8.4,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.