CVE-2026-21437 identifies a vulnerability in the eopkg package manager, a Python3-based tool used by the Solus Linux distribution. Versions prior to 4.4.0 lack proper support for integrity checking of installed package files, specifically allowing malicious packages to include files that are not tracked by eopkg's package database or visible through tools like lseopkg. This integrity check omission corresponds to CWE-353 (Missing Support for Integrity Check). An attacker who can convince a user to install a package from a malicious or compromised source can exploit this flaw to install hidden files on the system. These files could be used to maintain persistence, hide malicious payloads, or alter system behavior without detection by standard package management queries. The vulnerability requires user interaction to install the malicious package and elevated privileges (high privileges) to exploit, as indicated by the CVSS vector. The CVSS 4.0 base score is 2.0, reflecting low severity due to the limited attack vector (local), required privileges, and user interaction. No known exploits are currently reported in the wild. The issue was addressed in eopkg version 4.4.0 by adding proper integrity checks to ensure all installed files are tracked and visible to package management tools. Users who only install packages from official Solus repositories are not affected, as these repositories are trusted and presumably do not contain malicious packages.

For European organizations using Solus Linux and eopkg versions prior to 4.4.0, this vulnerability could allow attackers to install hidden files via malicious packages, potentially enabling stealthy persistence or unauthorized code execution. While the impact is limited by the need for user interaction and installation of untrusted packages, targeted attacks or supply chain compromises could exploit this to implant backdoors or malware that evade detection by package management tools. This could undermine system integrity and complicate incident response. However, the vulnerability does not affect availability or confidentiality directly and requires elevated privileges, limiting its exploitation scope. Organizations relying on official Solus repositories are not at risk, but those using third-party or custom package sources should be cautious. The overall impact on European organizations is low but non-negligible in environments where Solus is used in critical infrastructure or development systems.

European organizations should immediately upgrade all Solus systems using eopkg to version 4.4.0 or later to ensure the integrity check fix is applied. Strictly enforce the use of official Solus repositories and avoid installing packages from untrusted or third-party sources. Implement policies and user training to prevent installation of unverified packages. Employ file integrity monitoring solutions to detect unauthorized or hidden files on systems. Regularly audit installed packages and their files using updated tools that reflect the patched version of eopkg. Consider restricting administrative privileges to reduce the risk of unauthorized package installations. In environments where Solus is used, integrate package management monitoring into security incident and event management (SIEM) systems to detect anomalous package activities. Finally, maintain up-to-date backups to recover from potential compromise.