CVE-2021-4034
Red Hat Polkit Out-of-Bounds Read and Write Vulnerability
Red Hat Polkit
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.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 27 June 2022. US federal agencies were required to remediate it by 18 July 2022. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 94.9%, which is higher than 99.9% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2021-4034 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2021-4034.
What does CVE-2021-4034 affect?
CVE-2021-4034 affects Red Hat Polkit. 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.
How severe is CVE-2021-4034?
CVE-2021-4034 is rated HIGH with a CVSS base score of 7.8. EPSS puts the probability of exploitation in the next 30 days at 94.9%, higher than 99.9% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 18 July 2022.
How should organisations respond to CVE-2021-4034?
Apply the vendor patch for Red Hat Polkit as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.