CVE-2025-53819 is a high-severity vulnerability affecting Nix, a popular package manager used on Linux and other Unix-like systems, specifically impacting version 2.30.0. The vulnerability arises from improper privilege dropping during build execution on macOS systems. Normally, Nix builds should run under the build user's privileges to limit potential damage from malicious or compromised build scripts. However, in version 2.30.0, builds on macOS were erroneously executed with elevated root privileges instead of the intended lower-privileged build user. This flaw corresponds to CWE-271, which relates to errors in privilege lowering or dropping, leading to unintended privilege retention. The vulnerability allows an attacker who can trigger or influence a build process to execute arbitrary code with root privileges, potentially compromising system integrity and confidentiality. The CVSS v3.1 score is 7.9 (high), reflecting the significant impact on integrity and availability, with a local attack vector requiring low complexity and limited privileges but no user interaction. The scope is changed, indicating that the vulnerability affects resources beyond the initially compromised component. The issue was fixed in Nix version 2.30.1, but no known workarounds exist for affected systems still running 2.30.0. There are no known exploits in the wild as of the publication date, but the nature of the flaw makes it a critical concern for environments relying on Nix for package management and build automation on macOS.

For European organizations, especially those using Nix 2.30.0 on macOS for software development, continuous integration, or deployment pipelines, this vulnerability poses a significant risk. An attacker with local access or the ability to influence build inputs could escalate privileges to root, leading to full system compromise. This could result in unauthorized code execution, data tampering, or disruption of critical services. The integrity of software supply chains could be undermined, affecting trust in build artifacts and potentially leading to widespread downstream impacts. Organizations in sectors with stringent data protection requirements, such as finance, healthcare, and government, could face severe regulatory and reputational consequences if exploited. The lack of workarounds increases urgency for patching, and the vulnerability's presence in development environments could facilitate lateral movement or persistent footholds within networks.

European organizations should immediately audit their environments to identify any instances of Nix version 2.30.0 running on macOS systems. The primary mitigation is to upgrade to Nix 2.30.1 or later, where the privilege dropping issue is resolved. Since no workarounds exist, patching is critical. Additionally, organizations should enforce strict access controls around build environments, limiting who can trigger builds or modify build inputs. Implementing monitoring and alerting for unusual privilege escalations or root-level process executions during builds can help detect exploitation attempts. Employing sandboxing or containerization for build processes may provide an additional security layer. Regularly reviewing and hardening macOS security configurations, including System Integrity Protection (SIP) and user privilege assignments, will reduce the attack surface. Finally, organizations should integrate this vulnerability into their software supply chain risk assessments and incident response plans.