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CVE Record

CVE-2021-46906: HID: usbhid: fix info leak in hid_submit_ctrl

In the Linux kernel, the following vulnerability has been resolved: HID: usbhid: fix info leak in hid_submit_ctrl In hid_submit_ctrl(), the way of calculating the report length doesn't take into account that report->size can be zero. When running the syzkaller reproducer, a report of size 0 causes hid_submit_ctrl) to calculate transfer_buffer_length as 16384. When this urb is passed to the usb core layer, KMSAN reports an info leak of 16384 bytes. To fix this, first modify hid_report_len() to account for the zero report size case by using DIV_ROUND_UP for the division. Then, call it from hid_submit_ctrl().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

CVE-2021-46906 is a Linux kernel information leak in the USB HID driver path. A zero-size HID report can cause the kernel to handle an unexpectedly large 16,384-byte transfer buffer, exposing uninitialized memory according to KMSAN findings. Public sources do not provide a CVSS score or confirmed exploitation.

Executive priority

Treat this as a patch-management item, not an emergency, unless your environment permits untrusted USB HID device attachment on sensitive Linux systems. Severity evidence is incomplete, so prioritize based on kernel exposure and device-trust model.

Technical view

The issue is in hid_submit_ctrl() in Linux usbhid. Report length calculation failed to handle report->size equal to zero, allowing transfer_buffer_length to become 16384. The fix updates hid_report_len() to use DIV_ROUND_UP and calls it from hid_submit_ctrl().

Likely exposure

Exposure is most relevant to Linux systems running affected kernel versions with USB HID support. The bundle lists affected Linux kernel lines including 2.6.12 through 5.13-related stable lines, but distro backports may change exposure.

Exploitation context

The source cites a syzkaller reproducer and KMSAN-detected information leak. There is no KEV listing and no cited evidence of active exploitation, public weaponization, remote reachability, required privileges, or reliable exploitability.

Researcher notes

The key condition is report->size equal to zero causing incorrect length handling in hid_submit_ctrl(). The public record names syzkaller and KMSAN but does not provide exploitability boundaries, leak contents, or attacker prerequisites.

Mitigation direction

  • Update to a vendor kernel containing the referenced Linux stable fixes.
  • Check Linux distribution advisories for backported fixes and package status.
  • Prioritize systems accepting untrusted USB HID devices if patching is delayed.
  • Avoid claiming remediation complete until the vendor kernel includes the fix.

Validation and detection

  • Inventory deployed Linux kernel versions and vendor package builds.
  • Confirm whether affected systems use USB HID support or load usbhid.
  • Map each kernel build to vendor advisory or referenced stable commit status.
  • Track exceptions where distro backports obscure upstream version comparisons.
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

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ATT&CK lookup starting points

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CVE-2021-46906 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
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

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.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 4.4.274, 4.9.274, 4.14.238, 4.19.196, 5.4.127, 5.10.45, 5.12.12, 5.13affected
Weakness

CWE details

No CWE listed

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