CVE-2021-47178Network attack vector

Remote I/O stall via preemptible CPU-ID lookup

Published Mar 25, 2024 · Updated Aug 5, 2026

A preemptibility error in the Linux kernel SCSI target core allows remote attackers to stall iSCSI I/O with repeated SCSI commands. __target_init_cmd() calls smp_processor_id() from preemptible SCSI workqueue contexts, causing DEBUG_PREEMPT to emit a stack dump for every command. Exposure requires the SCSI target path and DEBUG_PREEMPT; unauthenticated iSCSI sessions can drive a log storm without disclosing or changing data.

CVSS severity7.5
High
EPSS probability0.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A preemptibility error in the Linux kernel SCSI target core allows remote attackers to stall iSCSI I/O with repeated SCSI commands. __target_init_cmd() calls smp_processor_id() from preemptible SCSI workqueue contexts, causing DEBUG_PREEMPT to emit a stack dump for every command. Exposure requires the SCSI target path and DEBUG_PREEMPT; unauthenticated iSCSI sessions can drive a log storm without disclosing or changing data.

The record

CVE
CVE-2021-47178
Published
Mar 25, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-459, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 25, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=008b936bbde3e87a611b3828a0d5d2a4f99026a0 <a222d2794c53f8165de20aa91b39e35e4b72bce9
  2. Affected versionversion=1526d9f10c6184031e42afad0adbdde1213e8ad1 <70ca3c57ff914113f681e657634f7fbfa68e1ad1
  3. Affected versionversion=1526d9f10c6184031e42afad0adbdde1213e8ad1 <a20b6eaf4f35046a429cde57bee7eb5f13d6857f
  4. Affected versionversion=5.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=008b936bbde3e87a611b3828a0d5d2a4f99026a0 <a222d2794c53f8165de20aa91b39e35e4b72bce9; version=1526d9f10c6184031e42afad0adbdde1213e8ad1 <70ca3c57ff914113f681e657634f7fbfa68e1ad1; version=1526d9f10c6184031e42afad0adbdde1213e8ad1 <a20b6eaf4f35046a429cde57bee7eb5f13d6857f; version=5.11

Published CVSS scores

7.5kernel.orgCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.5NIST NVDCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-459Incomplete Cleanup
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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