CVE-2025-37891 (GCVE-0-2025-37891)
Vulnerability from cvelistv5
Published
2025-05-19 07:19
Modified
2026-08-05 11:58
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: ALSA: ump: Fix buffer overflow at UMP SysEx message conversion The conversion function from MIDI 1.0 to UMP packet contains an internal buffer to keep the incoming MIDI bytes, and its size is 4, as it was supposed to be the max size for a MIDI1 UMP packet data. However, the implementation overlooked that SysEx is handled in a different format, and it can be up to 6 bytes, as found in do_convert_to_ump(). It leads eventually to a buffer overflow, and may corrupt the memory when a longer SysEx message is received. The fix is simply to extend the buffer size to 6 to fit with the SysEx UMP message.
References
Impacted products
Vendor Product Version
Linux Linux Version: 0b5288f5fe63eab687c14e5940b9e0d532b129f2
Version: 0b5288f5fe63eab687c14e5940b9e0d532b129f2
Version: 0b5288f5fe63eab687c14e5940b9e0d532b129f2
Version: 0b5288f5fe63eab687c14e5940b9e0d532b129f2
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{
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          "product": "Linux",
          "programFiles": [
            "include/sound/ump_convert.h"
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          ],
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          "vendor": "Linux",
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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\nALSA: ump: Fix buffer overflow at UMP SysEx message conversion\n\nThe conversion function from MIDI 1.0 to UMP packet contains an\ninternal buffer to keep the incoming MIDI bytes, and its size is 4, as\nit was supposed to be the max size for a MIDI1 UMP packet data.\nHowever, the implementation overlooked that SysEx is handled in a\ndifferent format, and it can be up to 6 bytes, as found in\ndo_convert_to_ump().  It leads eventually to a buffer overflow, and\nmay corrupt the memory when a longer SysEx message is received.\n\nThe fix is simply to extend the buffer size to 6 to fit with the SysEx\nUMP message."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The overflow is triggered by writing a MIDI 1.0 SysEx byte stream to the legacy rawmidi character device (/dev/snd/midiCxDy) that sound/core/ump.c creates for every UMP endpoint, reached via process_legacy_output() from an ordinary write(2). The alternate f_midi2 USB-gadget path is physical, but the local rawmidi path requires only local system access.\nAC:L - The attacker deterministically triggers the overflow by writing 0xF0 followed by five or more data bytes; the fifth byte directly overwrites the low byte of cvt-\u003elen, giving the attacker a chosen write offset with no race, no memory-layout guessing, and no retry logic.\nPR:L - Only an unprivileged local account with access to the ALSA MIDI device node is needed (audio group or active-seat uaccess ACL; an app with MIDI access on Android) \u2014 no capabilities, no root, and no privileged ioctl on the path.\nUI:N - The attacker writes to the MIDI device directly; no victim action is required. The presence of a UMP endpoint is an environmental precondition the attacker can satisfy themselves by attaching a USB MIDI 2.0 device or using an existing gadget/MIDI 2.0 interface.\nS:U - The corruption is confined to kernel heap memory within the same security authority; there is no VM, IOMMU, or sandbox boundary crossed.\nC:H - Attacker-controlled corruption of adjacent kmalloc-4k slab objects yields a read primitive by overwriting neighbouring length/pointer/index fields, and cvt_legacy_sysex_to_ump() additionally reads far out of bounds past the struct when a huge cvt-\u003elen is flushed.\nI:H - This is an unbounded linear out-of-bounds heap write with fully attacker-chosen data (one byte per SysEx byte, at an attacker-chosen starting offset), a classic slab-overflow primitive that can corrupt adjacent kernel objects and be escalated to arbitrary write and control-flow hijack.\nA:H - Walking off the end of the out_cvts allocation reliably corrupts slab metadata and neighbouring objects, causing oops/panic; the same write also destroys the converter\u0027s own state, so a trivial long SysEx message crashes the kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T11:58:06.907Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/ce4f77bef276e7d2eb7ab03a5d08bcbaa40710ec"
        },
        {
          "url": "https://git.kernel.org/stable/c/226beac5605afbb33f8782148d188b64396145a4"
        },
        {
          "url": "https://git.kernel.org/stable/c/42ef48dd4ebb082a1a90b5c3feeda2e68a9e32fe"
        },
        {
          "url": "https://git.kernel.org/stable/c/56f1f30e6795b890463d9b20b11e576adf5a2f77"
        }
      ],
      "title": "ALSA: ump: Fix buffer overflow at UMP SysEx message conversion",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-37891",
    "datePublished": "2025-05-19T07:19:04.583Z",
    "dateReserved": "2025-04-16T04:51:23.963Z",
    "dateUpdated": "2026-08-05T11:58:06.907Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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