CVE-2021-4034: PwnKit
Out-of-bounds Write: Is CVE-2021-4034 real, exploitable, or a false positive? Here's the community verdict.
signals
public sources
Confirmed exploited in the wild. Patch this first, regardless of the base score.
public exploits
links to sources — we don’t host codeA working exploit is publicly available from a maintained source. Treat this as higher urgency and verify your exposure.
baseline read
auto · not a community verdict
Real — exploited in the wild
CISA confirms active exploitation. Treat scanner hits as true positives unless your specific version or config is unaffected.
Based on CISA KEV
Confirm or dispute →CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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.
References
Published
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Field notes & remediation
Verdicts are the quick signal. Notes are the evidence and fixes behind them.
- 0
A flaw in how pkexec (part of polkit) handles its arguments gives a local user a trivial and essentially 100 percent reliable path to root. It was present in default installs for more than 12 years, needs no unusual conditions, and works on the standard configuration, so it is one of the first things an attacker tries after landing on any Linux host.
Who is affected: almost every Linux distribution with polkit installed, before the January 2022 fix.
How to check: compare the polkit or policykit package version against your distro's patched build.
Commonly flagged by: Nessus, Qualys, OpenVAS, Trivy.
- 0
Patch polkit to your distro's fixed version. If you truly cannot patch right away, a documented stopgap is to remove the setuid bit from pkexec with
chmod 0755 /usr/bin/pkexec, which breaks pkexec but stops the privilege escalation. Patch properly as soon as you can.
Add a field note or remediationoptional
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