On Friday, March 29, after investigating anomalous behavior in his Debian sid environment, developer Andres Freund contacted an open-source security mailing list to share that he had discovered an upstream backdoor in widely used command line tool XZ Utils (liblzma). The backdoor, added by an open-source committer who had been working on the tool for several years, affects XZ Utils versions 5.6.0 and 5.6.1. It has been assigned CVE-2024-3094.

According to Red Hat’s advisory –

“The malicious injection present in the xz versions 5.6.0 and 5.6.1 libraries is obfuscated and only included in full in the download package - the Git distribution lacks the M4 macro that triggers the build of the malicious code. The second-stage artifacts are present in the Git repository for the injection during the build time, in case the malicious M4 macro is present.

The resulting malicious build interferes with authentication in sshd via systemd.  SSH is a commonly used protocol for connecting remotely to systems, and sshd is the service that allows access.  Under the right circumstances this interference could potentially enable a malicious actor to break sshd authentication and gain unauthorized access to the entire system remotely.”

Community analysis of the backdoor is ongoing. Fortunately, thanks to Freund’s discovery, the backdoored version of the utility did not affect stable branches of most major Linux distributions and is unlikely to have made it into any production systems. The most at-risk category of users is likely developers, many of whom tend to run bleeding-edge versions of Linux.

Mitigation Guidance

XZ Utils u ..

Support the originator by clicking the read the rest link below.