CVE-2021-47306

Invalid kernel memory access via post-free logging

Published May 21, 2024 · Updated May 11, 2026

Use-after-free in the Linux FDDI DEFZA driver allows local users to trigger invalid kernel memory access during failed adapter probing. In fza_probe, the error path calls free_netdev() and then dereferences its freed device-private data while formatting an error message. Reachability requires DEFZA TURBOchannel adapter probing to fail; public records demonstrate no code execution or data disclosure consequence.

CVSS severity7.8
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux FDDI DEFZA driver allows local users to trigger invalid kernel memory access during failed adapter probing. In fza_probe, the error path calls free_netdev() and then dereferences its freed device-private data while formatting an error message. Reachability requires DEFZA TURBOchannel adapter probing to fail; public records demonstrate no code execution or data disclosure consequence.

The record

CVE
CVE-2021-47306
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1499.004
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

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Is a vulnerable build present?

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

  1. Affected versionversion=4.20
  2. Affected versionversion=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <04b06716838bfc26742dbed3ae1d3697fe5317ee
  3. Affected versionversion=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <bdfbb51f7a437ae8ea91317a5c133ec13adf3c47
  4. Affected versionversion=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <deb7178eb940e2c5caca1b1db084a69b2e59b4c9
  5. Affected versionversion=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <f33605908a9b6063525e9f68e62d739948c5fccf

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.20; version=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <04b06716838bfc26742dbed3ae1d3697fe5317ee; version=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <bdfbb51f7a437ae8ea91317a5c133ec13adf3c47; version=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <deb7178eb940e2c5caca1b1db084a69b2e59b4c9; version=61414f5ec9834df8aa4f55c90de16b71a3d6ca8d <f33605908a9b6063525e9f68e62d739948c5fccf

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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1499.004Application or System Exploitation

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

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Your stack

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