Finding Linux instances vulnerable to PwnKit

(updated ), by Pearce Barry
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News dropped this week around a memory corruption vulnerability with a broad reach across many Linux distributions, including Ubuntu, Debian, Mint, RHEL, Fedora, CentOS, Oracle, Arch, and SUSE. Having been present-but-unseen for over 12 years now, CVE-2021-4034 (with a “high” CVSS score of 7.8) resides in the PolKit (Policy Kit) component that is installed in many Linux distributions by default. Successful exploitation of this vulnerability provides a local privilege escalation (LPE) to hand over root-level privileges to an unprivileged user. Named PwnKit by the Qualys Research Team who discovered and disclosed the vulnerability, exploitation of vulnerable systems is considered to be straightforward and can purportedly be done without leaving an audit trail.

A number of major Linux distributions, including Ubuntu and Red Hat, recently released patches to fix this vulnerability, as well as the PolKit toolkit, itself. In the event that patching is not possible or patches are not available for an affected Linux install, a mitigation is suggested by the Qualys Research Team via removing the SUID bit from the pkexec program. Patching or mitigation of vulnerable systems is recommended, particularly with publicly available exploit code now available on the Internet.

How to find Linux instances potentially vulnerable to PwnKit with runZero #

From the Asset Inventory, use the following pre-built query to locate multi-user Linux assets within your network that are potentially vulnerable to PwnKit:

os:debian or os:ubuntu or os:mint or os:raspbian or os:="red hat%" or os:fedora or os:centos or os:cloudlinux or os:oracle or os:="arch%" or os:manjaro or os:suse
Find multi-user Linux servers

As always, any prebuilt queries we create are available from our Queries Library. Check out the library for other useful inventory queries.

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Pearce Barry
Written by Pearce Barry

Pearce Barry is a Director of Security Research at runZero. Barry joined runZero in June 2021, working on the Metasploit Project the four years prior. Now, Pearce leads research efforts at runZero, which includes creating and improving fingerprints, adding to protocols, enhancing scanning logic, and writing queries.

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