CVE-2021-47118

Kernel use-after-free via unreferenced cad_pid initialization

Published Mar 15, 2024 · Updated May 11, 2026

Use-after-free in Linux from 2.6.19 allows local users to access freed kernel memory through a write to the cad_pid sysctl. kernel_init_freeable assigns the init task's PID object to cad_pid without calling get_pid, so proc_do_cad_pid later calls put_pid on an unheld reference. Reaching the flaw requires local permission to modify the sysctl; later signal delivery can dereference the freed PID object and crash the kernel.

CVSS severity7.8
High
EPSS probability0.25%
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 from 2.6.19 allows local users to access freed kernel memory through a write to the cad_pid sysctl. kernel_init_freeable assigns the init task's PID object to cad_pid without calling get_pid, so proc_do_cad_pid later calls put_pid on an unheld reference. Reaching the flaw requires local permission to modify the sysctl; later signal delivery can dereference the freed PID object and crash the kernel.

The record

CVE
CVE-2021-47118
Published
Mar 15, 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. Mar 15, 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=2.6.19
  2. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <0711f0d7050b9e07c44bc159bbc64ac0a1022c7f
  3. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff
  4. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <4dbd8808a591b49b717862e6e0081bcf14a87788
  5. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <7178be006d495ffb741c329012da289b62dddfe6
  6. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <764c2e892d1fe895392aff62fb353fdce43bb529
  7. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <b8ff869f20152fbe66b6c2e2715d26a2f9897cca
  8. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <d106f05432e60f9f62d456ef017687f5c73cb414
  9. Affected versionversion=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <f86c80515a8a3703e0ca2e56deb50fc2879c5ea4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=2.6.19; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <0711f0d7050b9e07c44bc159bbc64ac0a1022c7f; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <4dbd8808a591b49b717862e6e0081bcf14a87788; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <7178be006d495ffb741c329012da289b62dddfe6; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <764c2e892d1fe895392aff62fb353fdce43bb529; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <b8ff869f20152fbe66b6c2e2715d26a2f9897cca; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <d106f05432e60f9f62d456ef017687f5c73cb414; version=9ec52099e4b8678a60e9f93e41ad87885d64f3e6 <f86c80515a8a3703e0ca2e56deb50fc2879c5ea4

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.

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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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