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Actively exploitedKnown ransomware use

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

The Red Hat polkit pkexec utility contains an out-of-bounds read and write vulnerability that allows for privilege escalation with administrative rights.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 27 Jun 2022.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated High severity (CVSS 7.8, scored by CISA).
  • It has been in the catalogue for 1,593 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

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 it'll induce pkexec to execute arbitrary code. When successfully executed the attack can cause a local privilege escalation given unprivileged users administrative rights on the target machine.

Affected Versions

ProductVersions
polkitall

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Red Hat Polkit. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated high, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 18 Jul 2022 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Red Hat Flaws

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CVE-2015-3246Red Hat Libuser Race Condition VulnerabilityAdded 26 Aug 2026CVE-2015-5287Red Hat Automatic Bug Reporting Tool Privilege Escalation VulnerabilityAdded 26 Aug 2026CVE-2018-14667Red Hat JBoss RichFaces Framework Expression Language Injection VulnerabilityAdded 28 Sep 2023CVE-2021-3560Red Hat Polkit Incorrect Authorization VulnerabilityAdded 12 May 2023CVE-2010-1428 · RansomwareRed Hat JBoss Information Disclosure VulnerabilityAdded 25 May 2022CVE-2010-0738 · RansomwareRed Hat JBoss Authentication Bypass VulnerabilityAdded 25 May 2022

All 9 exploited Red Hat vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2021-4034
  3. CVE record: CVE-2021-4034
  4. FIRST EPSS
  5. access.redhat.com/security/vulnerabilities/RHSB-2022-001
  6. qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt
  7. bugzilla.redhat.com/show_bug.cgi?id=2025869
  8. gitlab.freedesktop.org/polkit/polkit/-/commit/a2bf5c9c83b6ae46cbd5c779d3055bff81ded683
  9. oracle.com/security-alerts/cpuapr2022.html
  10. packetstormsecurity.com/files/166196/Polkit-pkexec-Local-Privilege-Escalation.html
  11. packetstormsecurity.com/files/166200/Polkit-pkexec-Privilege-Escalation.html
  12. suse.com/support/kb/doc/?id=000020564