On Friday, Red Hat issued a high-priority security alert regarding a discovery related to two versions of a widely-used data compression library called XZ Utils (formerly known as LZMA Utils). It was found that these specific versions of the library contained malicious code intentionally inserted by unauthorized parties. 

This code was designed with the malicious intent of allowing remote access to systems without authorization. This unauthorized access can lead to serious security threats to individuals and organizations utilizing these compromised versions of the library, potentially leading to data breaches or other malicious activities. 

The discovery and reporting of the issue have been attributed to Microsoft security researcher Andres Freund. It was revealed that the malicious code, which was heavily obfuscated, was introduced through a sequence of four commits made to the Tukaani Project on GitHub. These commits were attributed to a user named Jia Tan (JiaT75). 

XZ is a compression tool and library widely utilized on Unix-like systems such as Linux. It is renowned for its ability to significantly reduce file sizes while maintaining fast decompression speeds. This compression is achieved through the implementation of the LZMA (Lempel-Ziv-Markov chain algorithm) compression algorithm, which is well-regarded for its efficient compression ratios. 

The breach has garnered a critical CVSS score of 10.0, indicating the most severe level of threat. This vulnerability has been found to impact XZ Utils versions 5.6.0 and 5.6.1, which were released on February 24 and March 9, respectively. 

The Common Vulnerability Scoring System (CVSS) is a widely used tool in the cybersecurity sector, offering a standardized approach to evaluate the gravity of security vulnerabilities found in computer systems. Its main objective is to aid cybersecurity experts in prioritizing the resolution of these vulnerabilities based on their urgency. 

"Through a series of complex obfuscations, the liblzma build process extracts a prebuilt object file from a disguised test file existing in the source code, which is then used to modify specific functions in the liblzma code," an IBM subsidiary reported. 

Additionally, Red Hat clarified that while no versions of Red Hat Enterprise Linux (RHEL) are affected by this security flaw, evidence indicates successful injections within xz 5.6.x versions designed for Debian unstable (Sid). It is also noted that other Linux distributions may potentially be impacted by this vulnerability. 

In response to the security breach, the U.S. Cybersecurity and Infrastructure Security Agency (CISA) has taken action by issuing its own alert.  "CISA and the open source community are responding to reports of malicious code being embedded in XZ Utils versions 5.6.0 and 5.6.1. This activity was assigned CVE-2024-3094. XZ Utils is data compression software and may be present in Linux distributions. The malicious code may allow unauthorized access to affected systems".  

CISA is advising users to downgrade their XZ Utils installations to a version unaffected by the compromise. Specifically, they recommend reverting to an uncompromised version such as XZ Utils 5.4.6 Stable.