CVE-2021-47123

Kernel memory corruption via linked-timeout double free

Published Mar 15, 2024 · Updated Aug 5, 2026

Use-after-free in Linux kernel io_uring 5.11 through 5.12.9 allows local users to corrupt kernel memory via linked-timeout races. io_link_timeout_fn() can release a linked timeout on its failure path without removing it from the master request list, so master completion releases the same request again. The flaw is reachable by local users able to submit io_uring operations and can crash the host or compromise kernel execution.

CVSS severity7.8
High
EPSS probability0.22%
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 Linux kernel io_uring 5.11 through 5.12.9 allows local users to corrupt kernel memory via linked-timeout races. io_link_timeout_fn() can release a linked timeout on its failure path without removing it from the master request list, so master completion releases the same request again. The flaw is reachable by local users able to submit io_uring operations and can crash the host or compromise kernel execution.

The record

CVE
CVE-2021-47123
Published
Mar 15, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-416, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 15, 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=5.11
  2. Affected versionversion=90cd7e424969d29aff653333b4dcb4e2e199d791 <1f64f5e903b9d1d157875721e02adadc9d6f0a5d
  3. Affected versionversion=90cd7e424969d29aff653333b4dcb4e2e199d791 <447c19f3b5074409c794b350b10306e1da1ef4ba

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.11; version=90cd7e424969d29aff653333b4dcb4e2e199d791 <1f64f5e903b9d1d157875721e02adadc9d6f0a5d; version=90cd7e424969d29aff653333b4dcb4e2e199d791 <447c19f3b5074409c794b350b10306e1da1ef4ba

Published CVSS scores

7.8CanonicalCVSS: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 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
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

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Your stack

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