CVE-2021-4034Known exploitationPublic exploit

Root code execution via empty argument vector

Published Jan 28, 2022 · Updated Aug 15, 2026

Local privilege escalation in Polkit pkexec allows local users to execute arbitrary code as root through crafted environment variables. With argc set to zero, pkexec reads envp[0] out of bounds as argv[1], then writes a resolved program path back into the environment array. Any unprivileged user with local login access can exploit the setuid-root binary and gain full administrative control.

CVSS severity7.8
High
EPSS probability94.92%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Local privilege escalation in Polkit pkexec allows local users to execute arbitrary code as root through crafted environment variables. With argc set to zero, pkexec reads envp[0] out of bounds as argv[1], then writes a resolved program path back into the environment array. Any unprivileged user with local login access can exploit the setuid-root binary and gain full administrative control.

The record

CVE
CVE-2021-4034
Published
Jan 28, 2022
Updated
Aug 15, 2026
Vendor
Libslirp Project
Product
Polkit
Classifications
CWE-787, CWE-125, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 28, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 15, 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=all

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Libslirp Project · Polkitversion=all

Published CVSS scores

7.2NIST NVDAV:L/AC:L/Au:N/C:C/I:C/A:C
7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-125Out-of-bounds Read
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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