CVE-2021-39648

Kernel heap disclosure via unlocked UDC read

Published Dec 15, 2021 · Updated Aug 4, 2024

Information disclosure in the Android Linux kernel allows local users with System privileges to read kernel heap memory through USB gadget configfs. gadget_dev_desc_UDC_show reads udc_name while unregister_gadget can free it in another context because the read lacks the mutex added by the patch. The race requires System-level local access and no user interaction; disclosed bytes can expose stale kernel heap contents but do not provide code execution.

CVSS severity4.1
Medium
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the Android Linux kernel allows local users with System privileges to read kernel heap memory through USB gadget configfs. gadget_dev_desc_UDC_show reads udc_name while unregister_gadget can free it in another context because the read lacks the mutex added by the patch. The race requires System-level local access and no user interaction; disclosed bytes can expose stale kernel heap contents but do not provide code execution.

The record

CVE
CVE-2021-39648
Published
Dec 15, 2021
Updated
Aug 4, 2024
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-362
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Dec 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=Android kernel

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

The Linux Kernel Organization · Linux Kernelversion=Android kernel

Published CVSS scores

1.9NIST NVDAV:L/AC:M/Au:N/C:P/I:N/A:N
4.1NIST NVDCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N

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.

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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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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