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CVE Record

CVE-2025-38556: HID: core: Harden s32ton() against conversion to 0 bits

In the Linux kernel, the following vulnerability has been resolved: HID: core: Harden s32ton() against conversion to 0 bits Testing by the syzbot fuzzer showed that the HID core gets a shift-out-of-bounds exception when it tries to convert a 32-bit quantity to a 0-bit quantity. Ideally this should never occur, but there are buggy devices and some might have a report field with size set to zero; we shouldn't reject the report or the device just because of that. Instead, harden the s32ton() routine so that it returns a reasonable result instead of crashing when it is called with the number of bits set to 0 -- the same as what snto32() does.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2025-38556 is a Linux kernel HID flaw where a malformed or buggy HID device report can trigger a kernel shift-out-of-bounds exception. The known impact from the source is a crash scenario, not data theft or remote compromise. Public severity and CVSS details are not provided.

Executive priority

Treat this as a kernel reliability risk with unclear severity. Prioritize patch verification for workstations, kiosks, labs, and systems exposed to many peripherals, but do not treat it as confirmed active exploitation based on the supplied evidence.

Technical view

The Linux HID core function s32ton() could be called with a bit width of 0 while converting a 32-bit value. Syzbot found this caused a shift-out-of-bounds exception. The kernel fix hardens s32ton() to return a reasonable result for 0-bit conversion, matching snto32() behavior.

Likely exposure

Exposure is most relevant to Linux systems that process HID input from devices whose report fields may be malformed or size zero. The provided affected data lists Linux kernel versions and stable commits, but does not clearly map every distribution package or product build.

Exploitation context

The bundle does not show active exploitation, and KEV is false. The evidence points to fuzzing-discovered crash behavior triggered by malformed HID report handling. No public exploit status, attacker prerequisites, or real-world abuse details are provided in the supplied sources.

Researcher notes

Focus validation on HID report parsing paths and whether s32ton() handles zero-bit conversion safely. The source indicates syzbot coverage and a targeted hardening change; it does not provide CVSS, CWE, proof-of-concept details, or distribution-specific fixed builds.

Mitigation direction

  • Update to a Linux kernel containing the referenced stable HID fix.
  • Check distribution advisories for patched kernel packages covering CVE-2025-38556.
  • Limit use of untrusted HID devices where operationally feasible.
  • Prioritize systems that accept frequent or uncontrolled peripheral connections.

Validation and detection

  • Inventory Linux kernel versions across affected fleets.
  • Confirm whether installed kernels include one of the referenced stable commits.
  • Review distro CVE advisories for package-specific fixed versions.
  • Test representative systems after kernel updates with normal HID peripherals.
Prepared
Confidence
medium
Sources
10

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.

ATT&CK lookup starting points

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CVE-2025-38556 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
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.

0CVSS vectors
3Timeline events
0ADP providers
9Source links

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
LinuxLinuxdde5845a529ff753364a6d1aea61180946270bfa, dde5845a529ff753364a6d1aea61180946270bfa, dde5845a529ff753364a6d1aea61180946270bfa, dde5845a529ff753364a6d1aea61180946270bfa, dde5845a529ff753364a6d1aea61180946270bfa, dde5845a529ff753364a6d1aea61180946270bfa, dde5845a529ff753364a6d1aea61180946270bfa, dde5845a529ff753364a6d1aea61180946270bfaunaffected
LinuxLinux2.6.20, 0, 5.10.248, 5.15.198, 6.1.159, 6.6.119, 6.12.46, 6.15.10, 6.16.1, 6.17affected
Weakness

CWE details

No CWE listed

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