CVE-2021-4034: Red Hat Polkit Out-of-Bounds Read and Write Vulnerability

Patch now

HIGH 7.8EXPLOITEDWATCHLISTUPGRADEDOWNGRADEMITIGATE

CVE-2021-4034 is a high-severity flaw (CVSS 7.8) affecting polkit, enterprise linux server update services for sap solutions, enterprise linux, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A local privilege escalation vulnerability was found on polkit's pkexec utility. The pkexec application is a setuid tool designed to allow unprivileged users to run commands as privileged users according predefined policies. The current version of pkexec doesn't handle the calling parameters count correctly and ends trying to execute environment variables as commands. An attacker can leverage this by crafting environment variables in such a way i

Why this priority

High severity
EPSS top 1%: very likely to be exploited
Exploited in the wild (CISA KEV)
Used in ransomware campaigns
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	94.9% (top 1%)
CISA exploited list	Yes, fix due 2022-07-18, used in ransomware
Weakness	CWE-787, CWE-125
Published	2022-01-28
Last modified	2026-08-15

Publisher (CNA): Red Hat, Inc. · Vendor: polkit project · redhat

Last updated 2026-08-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-01-28 20:15 UTCPublished CVE record published
2022-06-27Exploited Added to the CISA Known Exploited Vulnerabilities list
2022-07-18Deadline CISA due date for US federal agencies to patch
2026-08-15 04:17 UTCUpdated Record last modified

polkit project polkit UPGRADE

Affected: < 121

Fixed in: 121

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy polkit || rpm -q polkit || polkit --version

2. UPGRADE to 121 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade polkit

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade polkit

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

redhat enterprise linux server update services for sap solutions DOWNGRADE

Affected: 7.6 · 7.7

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.6

1. Check installed version

apt-cache policy enterprise-linux-server-update-services-for-sap-solutions || rpm -q enterprise-linux-server-update-services-for-sap-solutions || enterprise-linux-server-update-services-for-sap-solutions --version

2. No fixed release: DOWNGRADE to a release before 7.6 (Debian / Ubuntu)

apt-cache madison enterprise-linux-server-update-services-for-sap-solutions sudo apt install enterprise-linux-server-update-services-for-sap-solutions=<VERSION_BEFORE_7.6> sudo apt-mark hold enterprise-linux-server-update-services-for-sap-solutions

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list enterprise-linux-server-update-services-for-sap-solutions sudo dnf downgrade enterprise-linux-server-update-services-for-sap-solutions-<VERSION_BEFORE_7.6> sudo dnf versionlock add enterprise-linux-server-update-services-for-sap-solutions

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

redhat enterprise linux MITIGATE

Affected: 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux desktop MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux eus MITIGATE

Affected: 8.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.2

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux for ibm z systems MITIGATE

Affected: 7.0 · 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · nemo · FIXED · 6.8.0-1.fc46 · FEDORA-2026-0edead723f · source

sudo dnf upgrade --advisory=FEDORA-2026-0edead723f

Fedora ELN · composer · FIXED · 2.11.1-1.eln159 · FEDORA-2026-cb4f992456 · source

sudo dnf upgrade --advisory=FEDORA-2026-cb4f992456

Ubuntu 20.04 · policykit-1 · FIXED · 0.105-26ubuntu1.2

sudo apt update && sudo apt install --only-upgrade policykit-1 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' policykit-1)" ge "0.105-26ubuntu1.2" && echo PATCHED || echo STILL-VULNERABLE

Ubuntu 22.04 · policykit-1 · FIXED · 0.105-31ubuntu1

sudo apt update && sudo apt install --only-upgrade policykit-1 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' policykit-1)" ge "0.105-31ubuntu1" && echo PATCHED || echo STILL-VULNERABLE

Debian 12 · policykit-1 · FIXED · 0.105-31.1

sudo apt update && sudo apt install --only-upgrade policykit-1 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' policykit-1)" ge "0.105-31.1" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · policykit-1 · FIXED · 0.105-31.1

sudo apt update && sudo apt install --only-upgrade policykit-1 dpkg --compare-versions "$(dpkg-query -W -f='${Version}' policykit-1)" ge "0.105-31.1" && echo PATCHED || echo STILL-VULNERABLE

RHEL 6 Extended Lifecycle Support · polkit · FIXED · polkit-0.96-11.el6_10.2

sudo dnf upgrade --advisory=RHSA-2022:0269 rpm -q polkit

RHEL 7 · polkit · FIXED · polkit-0.112-26.el7_9.1

sudo dnf upgrade --advisory=RHSA-2022:0274 rpm -q polkit

RHEL 7.3 Advanced Update Support · polkit · FIXED · polkit-0.112-12.el7_3.1

sudo dnf upgrade --advisory=RHSA-2022:0270 rpm -q polkit

RHEL 7.4 Advanced Update Support · polkit · FIXED · polkit-0.112-12.el7_4.2

sudo dnf upgrade --advisory=RHSA-2022:0272 rpm -q polkit

RHEL 7.6 Advanced Update Support · polkit · FIXED · polkit-0.112-18.el7_6.3

sudo dnf upgrade --advisory=RHSA-2022:0271 rpm -q polkit

Alpine 3.20 · polkit · FIXED · polkit-0.120-r2

apk add --upgrade polkit apk info -v polkit

Alpine 3.21 · polkit · FIXED · polkit-0.120-r2

apk add --upgrade polkit apk info -v polkit

Alpine 3.22 · polkit · FIXED · polkit-0.120-r2

apk add --upgrade polkit apk info -v polkit

Alpine 3.23 · polkit · FIXED · polkit-0.120-r2

apk add --upgrade polkit apk info -v polkit

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2023-026 · source

sudo dnf update --advisory=ALAS2023-2023-026

Amazon Linux 2 · see advisory · FIXED · ALAS2-2022-1745 · source

sudo yum update --advisory=ALAS2-2022-1745

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: berdav/CVE-2021-4034 (2047 stars)
GitHub PoC: ly4k/PwnKit (1338 stars)
GitHub PoC: arthepsy/CVE-2021-4034 (1174 stars)
Write-up: www.oracle.com/security-alerts/cpuapr2022.html
Write-up: www.secpod.com/blog/local-privilege-escalation-vulnerability-in-major-linux-distributions-
GitHub PoC: 0x01-sec/CVE-2021-4034-
Exploit-DB: PolicyKit-1 0.105-31 - Privilege Escalation
Metasploit: Local Privilege Escalation in polkits pkexec

Verify at the official source NVD · CVE Program · CISA KEV catalog · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-4034?

polkit: upgrade to 121; enterprise linux server update services for sap solutions: downgrade or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-4034 being exploited?

Yes. CVE-2021-4034 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2021-4034 affect?

CVE-2021-4034 affects polkit, enterprise linux server update services for sap solutions, enterprise linux. Severity is high (CVSS 7.8). A local privilege escalation vulnerability was found on polkit's pkexec utility. The pkexec application is a setuid tool designed to allow unprivileged users to run commands as privileged users according predefined policies. The current ver

How urgent is CVE-2021-4034?

Priority 92/100. High severity; EPSS top 1%: very likely to be exploited; Exploited in the wild (CISA KEV); Used in ransomware campaigns; Public exploit reference; On your watchlist

Software pages

SAP vulnerabilities

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CVE-2021-3560 HIGH 7.8 EXPLOITED UPGRADE MITIGATE Red Hat Polkit Incorrect Authorization Vulnerability

References

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