Summary
A high severity (CVSS: 7.8) vulnerability has been identified in the GNU C Library. Identified as CVE-2023-4911, nicknamed Looney Tunables, it was recently added to CISA’s Known Exploited Vulnerabilities catalogue because it is now being actively exploited. This buffer overflow vulnerability makes use of a flaw within the libraries’ dynamic loader and GLIBC_TUNABLES environment variable. This can allow a local attacker to use specifically crafted GLIBC_TUNABLES environment variables while launching binaries with SUID permission to execute code with elevated privileges.
Impact Assessment
This vulnerability impacts a collection of open-source libraries which are used with the unix-like GNU operating system and other systems that utilize the Linux kernel. If exploited, it will allow an attacker to execute code with SUID, a Linux/Unix term allowing a program or script to run with elevated privileges. As with any exploitation or attack, the attacker’s goal is almost always to elevate privilege to gain further access to the system and with this attack it allows escalation to root privileges, the highest operating system level. The only silver lining to this vulnerability is that it requires the attacker’s attack vector to be local which means mitigations can be put in place to prevent this from being exploited.
Affected products
According to Qualys, the CNE who discovered this vulnerability, this vulnerability affects all distributions that use the GNU C Library. They have personally identified that Fedora 37 and 38, Ubuntu 22.04 and 23.04, and Devian 12 and 13 are susceptible.
What it means for you
Review your organization’s asset inventory and identify any susceptible Linux distributions which use the GNU C Library. If you identify any distributions of Linux which use the library begin performing patching procedures as soon as possible.
Remediation
There are patches available for the Looney Tunables vulnerability. See your Linux distribution and apply operating system patches.
Business Implications
Exploitation of this vulnerability will allow an attacker full access to the system allowing them to install malware and change configurations on the system. This could potentially allow the attacker to traverse through the network allowing for a much worse attack if proper network segmentation is not in place. There will be monetary, reputational, and data loss as a result depending on what the system is used for, what data is on the system, and the criticality of the system to business operations.
Access Point Technology Recommends
Patch: There are patches available for many Linux distributions which will patch this vulnerability. Identify which systems are vulnerable to CVE-2023-4911 and patch as soon as possible.
Segment Network: Having a proper network infrastructure and configuration will prevent this attack from being as impactful if exploited.
Access Control: Due to this vulnerability having a local attack vector, controlling who has access to certain systems in your organization can prevent this type of attack from occurring.
Associated Bulletins
https://www.cisa.gov/known-exploited-vulnerabilities-catalog
https://nvd.nist.gov/vuln/detail/CVE-2023-4911
https://blog.qualys.com/vulnerabilities-threat-research/2023/10/03/cve-2023-4911-looney-tunables-local-privilege-escalation-in-the-glibcs-ld-so
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