CVE-2021-47333

Kernel oops via null PCI bridge dereference

Published May 21, 2024 · Updated May 11, 2026

NULL pointer dereference in the Linux kernel allows local users to cause a kernel oops by probing a directly attached Alcor card reader. The alcor_pci probe path passes a null parent PCI device to alcor_pci_init_check_aspm when bus->self is null at the root complex, leading pci_read_config_byte to dereference it. Reachability requires an Alcor controller attached directly to the root complex; the resulting oops can interrupt the host.

CVSS severity5.5
Medium
EPSS probability0.24%
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

NULL pointer dereference in the Linux kernel allows local users to cause a kernel oops by probing a directly attached Alcor card reader. The alcor_pci probe path passes a null parent PCI device to alcor_pci_init_check_aspm when bus->self is null at the root complex, leading pci_read_config_byte to dereference it. Reachability requires an Alcor controller attached directly to the root complex; the resulting oops can interrupt the host.

The record

CVE
CVE-2021-47333
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, 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

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=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <09d154990ca82d14aed2b72796f6c8845e2e605d
  2. Affected versionversion=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <3ce3e45cc333da707d4d6eb433574b990bcc26f5
  3. Affected versionversion=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <58f69684ba03e5b0e0a3ae844a845280c0f06309
  4. Affected versionversion=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <717cf5ae52322ddbdf3ac2c584b34c5970b0d174
  5. Affected versionversion=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <d2639ffdcad463b358b6bef8645ff81715daffcb
  6. Affected versionversion=5.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <09d154990ca82d14aed2b72796f6c8845e2e605d; version=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <3ce3e45cc333da707d4d6eb433574b990bcc26f5; version=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <58f69684ba03e5b0e0a3ae844a845280c0f06309; version=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <717cf5ae52322ddbdf3ac2c584b34c5970b0d174; version=4f556bc04e3c0de2f5c69adc9e9f2bcefcad079d <d2639ffdcad463b358b6bef8645ff81715daffcb; version=5.0

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

CWE-476NULL Pointer Dereference
T1499.004Endpoint Denial of Service: Application 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

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