CVE-2026-21436 is a path traversal vulnerability (CWE-24) found in eopkg, the package manager for the Solus Linux distribution, implemented in Python3. In versions prior to 4.4.0, when a user installs a package using the --destdir option to specify a custom installation directory, a malicious package can exploit insufficient path sanitization to escape this directory. Instead of installing files within the intended directory, the package can write files to arbitrary locations on the host filesystem. This can be leveraged by an attacker to overwrite critical system files, plant malicious binaries, or modify configuration files, potentially leading to privilege escalation or system compromise. Exploitation requires the installation of a malicious or compromised package, high privileges (as the package manager typically runs with elevated rights), and user interaction to initiate the installation. The vulnerability does not affect users who install packages exclusively from the official Solus repositories, as these are assumed to be trusted. The issue was addressed and fixed in eopkg version 4.4.0 by properly sanitizing and restricting file paths during package installation. The CVSS v4.0 score is 5.8 (medium severity), reflecting the local attack vector, required privileges, and user interaction, with high impact on integrity and availability but no impact on confidentiality. No known exploits have been reported in the wild as of the publication date.

For European organizations using Solus Linux and eopkg versions prior to 4.4.0, this vulnerability poses a risk of unauthorized file system modifications during package installation. Attackers who can convince users or administrators to install malicious or compromised packages can leverage this flaw to write files outside the intended directory, potentially overwriting system binaries, configuration files, or planting persistent malware. This can lead to system instability, privilege escalation, or a foothold for further attacks. While the attack requires local access or social engineering to install a malicious package, the impact on system integrity and availability is significant. Organizations relying on Solus Linux in development, research, or specialized environments may face operational disruptions or security breaches. Since the vulnerability does not affect users installing only from official repositories, the risk is mitigated for organizations with strict package source controls. However, environments that allow third-party or custom package installations are at higher risk. The lack of known exploits in the wild reduces immediate threat but does not eliminate the risk of targeted attacks or future exploit development.

European organizations should immediately upgrade eopkg to version 4.4.0 or later to remediate this vulnerability. They should enforce strict policies to install packages only from trusted, official Solus repositories and avoid using third-party or unverified package sources. Implementing application whitelisting and integrity checking on installed packages can help detect unauthorized modifications. When using the --destdir option, administrators should validate and sanitize input paths and monitor installation logs for suspicious activity. Employing least privilege principles by limiting the use of elevated privileges during package installation can reduce exploitation risk. Regularly auditing installed packages and system files for unexpected changes will aid in early detection of compromise. Additionally, educating users and administrators about the risks of installing untrusted packages and the importance of updates is critical. Network segmentation and endpoint protection can further reduce the attack surface. Finally, maintain up-to-date backups to recover from potential system corruption or compromise.