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CVE Record

CVE-2025-37891: ALSA: ump: Fix buffer overflow at UMP SysEx message conversion

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.

HighCVSS 7.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in the Linux kernel’s ALSA MIDI handling can overwrite memory when converting longer MIDI System Exclusive messages. A local user with low privileges could potentially crash the system or compromise confidentiality and integrity. The supplied assessment scores it 7.8 (High), but the sources do not report active exploitation.

Executive priority

Treat this as a high-priority kernel update for exposed multi-user or MIDI-processing systems, especially where untrusted local users exist. It is not presented as an internet-remote vulnerability, and active exploitation is unconfirmed. Use normal emergency-change judgment based on local-user access, ALSA UMP usage, and distribution guidance.

Technical view

The MIDI 1.0-to-UMP conversion stored incoming bytes in a four-byte internal buffer, while SysEx UMP data can require six bytes. Processing a longer SysEx message could therefore corrupt kernel memory. The cited Linux stable fixes enlarge the buffer to six bytes. The CVSS vector indicates local access, low complexity, low privileges, no user interaction, and high impacts.

Likely exposure

Exposure is most relevant to Linux systems where a low-privileged local user can reach the affected ALSA UMP MIDI conversion path. Systems without that pathway in use may have lower practical exposure. The supplied affected-version data is not sufficiently clear for reliable range interpretation, so confirm status through kernel or distribution advisories and fix-commit inclusion.

Exploitation context

The supplied CVSS vector describes a local, low-complexity attack requiring low privileges and no user interaction. Successful exploitation could affect confidentiality, integrity, and availability. CVE-2025-37891 is not identified as a CISA KEV entry in the bundle, and none of the cited sources establishes active exploitation or a public exploit.

Researcher notes

The root cause is a size mismatch between a four-byte conversion buffer and SysEx UMP data of up to six bytes. The fix increases the buffer to six bytes. The source bundle supplies four stable-tree commits but does not clearly map each commit to an exact corrected release range; validate backports by commit or vendor advisory.

Mitigation direction

  • Update to a vendor-supported kernel containing the applicable cited stable fix.
  • Check the Linux distribution’s advisory for corrected package versions and required reboot guidance.
  • Prioritize multi-user systems offering untrusted users access to ALSA MIDI or UMP functionality.
  • If updating is delayed, consult vendor guidance for supported temporary exposure-reduction measures.

Validation and detection

  • Inventory running kernel versions on systems providing ALSA MIDI or UMP functionality.
  • Confirm whether the running kernel contains the applicable cited fix commit or vendor backport.
  • Verify the corrected kernel is running after installation, including after any required reboot.
  • Review distribution advisories because the supplied affected-version list has ambiguous boundaries.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

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CVE-2025-37891 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
5Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2025-37891Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux0b5288f5fe63eab687c14e5940b9e0d532b129f2, 0b5288f5fe63eab687c14e5940b9e0d532b129f2, 0b5288f5fe63eab687c14e5940b9e0d532b129f2, 0b5288f5fe63eab687c14e5940b9e0d532b129f2unaffected
LinuxLinux6.5, 0, 6.6.90, 6.12.28, 6.14.6, 6.15affected
Weakness

CWE details

No CWE listed

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