CVE-2021-47231

Kernel-memory leak via unreleased USB buffers

Published May 21, 2024 · Updated May 11, 2026

A memory leak in the Linux kernel mcba_usb CAN driver from 4.12 allows local users to consume kernel memory by cycling an attached USB device. The mcba_usb_start() path allocates 20 coherent USB buffers, but callbacks only resubmit URBs and disconnect kills them without calling usb_free_coherent(). Triggering the leak requires a Microchip CAN BUS Analyzer Tool and repeated device lifecycle events; each cycle leaves the demonstrated allocations resident.

CVSS severity5.5
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

A memory leak in the Linux kernel mcba_usb CAN driver from 4.12 allows local users to consume kernel memory by cycling an attached USB device. The mcba_usb_start() path allocates 20 coherent USB buffers, but callbacks only resubmit URBs and disconnect kills them without calling usb_free_coherent(). Triggering the leak requires a Microchip CAN BUS Analyzer Tool and repeated device lifecycle events; each cycle leaves the demonstrated allocations resident.

The record

CVE
CVE-2021-47231
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=4.12
  2. Affected versionversion=51f3baad7de943780ce0c17bd7975df567dd6e14 <6bd3d80d1f019cefa7011056c54b323f1d8b8e83
  3. Affected versionversion=51f3baad7de943780ce0c17bd7975df567dd6e14 <6f87c0e21ad20dd3d22108e33db1c552dfa352a0
  4. Affected versionversion=51f3baad7de943780ce0c17bd7975df567dd6e14 <89df95ce32be204eef2e7d4b2f6fb552fb191a68
  5. Affected versionversion=51f3baad7de943780ce0c17bd7975df567dd6e14 <91c02557174be7f72e46ed7311e3bea1939840b0
  6. Affected versionversion=51f3baad7de943780ce0c17bd7975df567dd6e14 <a115198caaab6d663bef75823a3c5f0802306d60
  7. Affected versionversion=51f3baad7de943780ce0c17bd7975df567dd6e14 <d0760a4ef85697bc756d06eae17ae27f3f055401

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.12; version=51f3baad7de943780ce0c17bd7975df567dd6e14 <6bd3d80d1f019cefa7011056c54b323f1d8b8e83; version=51f3baad7de943780ce0c17bd7975df567dd6e14 <6f87c0e21ad20dd3d22108e33db1c552dfa352a0; version=51f3baad7de943780ce0c17bd7975df567dd6e14 <89df95ce32be204eef2e7d4b2f6fb552fb191a68; version=51f3baad7de943780ce0c17bd7975df567dd6e14 <91c02557174be7f72e46ed7311e3bea1939840b0; version=51f3baad7de943780ce0c17bd7975df567dd6e14 <a115198caaab6d663bef75823a3c5f0802306d60; version=51f3baad7de943780ce0c17bd7975df567dd6e14 <d0760a4ef85697bc756d06eae17ae27f3f055401

Published CVSS scores

5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.001OS Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo