CVE-2021-47239

Kernel memory corruption via uncanceled multicast work

Published May 21, 2024 · Updated May 11, 2026

Use-after-free in the Linux kernel SMSC75xx USB network driver allows local users to corrupt kernel memory during device binding. smsc75xx_bind leaves multicast work queued during failed bind cleanup, so smsc75xx_set_multicast can access the freed device after deallocation. The race requires queued work to start after cleanup; successful exploitation can crash the kernel or modify protected kernel data.

CVSS severity7.8
High
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

Use-after-free in the Linux kernel SMSC75xx USB network driver allows local users to corrupt kernel memory during device binding. smsc75xx_bind leaves multicast work queued during failed bind cleanup, so smsc75xx_set_multicast can access the freed device after deallocation. The race requires queued work to start after cleanup; successful exploitation can crash the kernel or modify protected kernel data.

The record

CVE
CVE-2021-47239
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068
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=200dbfcad8011e50c3cec269ed7b980836eeb1fa <7cc8b2e05fcea6edd022d26e82091d781af8fd9b
  2. Affected versionversion=22c840596af0c09068b6cf948616e6496e59e07f <64160d1741a3de5204d1a822e058e0b4cc526504
  3. Affected versionversion=4.14.235 <4.14.238
  4. Affected versionversion=4.19.193 <4.19.196
  5. Affected versionversion=4.4.271 <4.4.274
  6. Affected versionversion=46a8b29c6306d8bbfd92b614ef65a47c900d8e70 <56b786d86694e079d8aad9b314e015cd4ac02a3d
  7. Affected versionversion=4.9.271 <4.9.274
  8. Affected versionversion=5.10.42 <5.10.46
  9. Affected versionversion=5.12.9 <5.12.13
  10. Affected versionversion=5.4.124 <5.4.128
  11. Affected versionversion=635ac38b36255d3cfb8312cf7c471334f4d537e0 <570a52cf3e01d19f7fd1a251dfc52b0cd86c13cb
  12. Affected versionversion=70c886ac93f87ae7214a0c69151a28a8075dd95b <14616c372a7be01a2fb8c56c9d8debd232b9e43d
  13. Affected versionversion=9e6a3eccb28779710cbbafc4f4258d92509c6d07 <2fc8300c9cfa5167fcb5b1a2a07db6f53e82f59b
  14. Affected versionversion=9e6b8c1ff9d997e1fa16cbd2d60739adf6dc1bbc <c4e3be2e7742863e454ce31faf8fd0109c00050b
  15. Affected versionversion=b95fb96e6339e34694dd578fb6bde3575b01af17 <4252bf6c2b245f47011098113d405ffad6ad5d5b

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=200dbfcad8011e50c3cec269ed7b980836eeb1fa <7cc8b2e05fcea6edd022d26e82091d781af8fd9b; version=22c840596af0c09068b6cf948616e6496e59e07f <64160d1741a3de5204d1a822e058e0b4cc526504; version=4.14.235 <4.14.238; version=4.19.193 <4.19.196; version=4.4.271 <4.4.274; version=46a8b29c6306d8bbfd92b614ef65a47c900d8e70 <56b786d86694e079d8aad9b314e015cd4ac02a3d; version=4.9.271 <4.9.274; version=5.10.42 <5.10.46; version=5.12.9 <5.12.13; version=5.4.124 <5.4.128; version=635ac38b36255d3cfb8312cf7c471334f4d537e0 <570a52cf3e01d19f7fd1a251dfc52b0cd86c13cb; version=70c886ac93f87ae7214a0c69151a28a8075dd95b <14616c372a7be01a2fb8c56c9d8debd232b9e43d; version=9e6a3eccb28779710cbbafc4f4258d92509c6d07 <2fc8300c9cfa5167fcb5b1a2a07db6f53e82f59b; version=9e6b8c1ff9d997e1fa16cbd2d60739adf6dc1bbc <c4e3be2e7742863e454ce31faf8fd0109c00050b; version=b95fb96e6339e34694dd578fb6bde3575b01af17 <4252bf6c2b245f47011098113d405ffad6ad5d5b

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1068Exploitation for Privilege Escalation

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