CVE-2023-49298 is a vulnerability affecting OpenZFS storage systems in versions up to 2.1.13 and 2.2.x through 2.2.1. The issue manifests during certain file copy operations where applications depend on efficient data copying mechanisms provided by OpenZFS. Under these conditions, the file contents can be replaced with zero-valued bytes instead of the expected data. This behavior can inadvertently disable security controls that rely on file contents, such as access control lists or deny rules configured in files like /etc/hosts.deny. The vulnerability is linked to improper handling of file data during copy-on-write or similar operations, categorized under CWE-639 (Authorization Bypass Through User-Controlled Key). While not always security-critical, realistic scenarios exist where this can lead to security bypasses. The flaw is less prevalent in version 2.2.1 and earlier than 2.1.4 due to default configuration changes that mitigate the issue. The CVSS 3.1 score of 7.5 reflects a network attack vector with low attack complexity, no privileges or user interaction required, and a high impact on integrity but no impact on confidentiality or availability. No public exploits have been reported yet, but the potential for disabling critical security mechanisms makes this a significant risk for systems relying on OpenZFS for secure file storage and copying.

For European organizations, the impact of CVE-2023-49298 can be substantial, especially in sectors that rely heavily on OpenZFS for data storage and integrity, such as government, finance, telecommunications, and critical infrastructure. The vulnerability can lead to unauthorized modification of critical configuration files or security policies by replacing their contents with zeros, effectively disabling security controls without detection. This can result in unauthorized access, privilege escalation, or denial of security enforcement, undermining the confidentiality and integrity of sensitive data. Since the vulnerability does not affect availability directly, service disruption is less likely, but the silent corruption of security-related files poses a serious risk. Organizations using automated file copy operations or backup tools that rely on OpenZFS's efficient copying mechanisms are particularly vulnerable. The lack of required authentication and user interaction means attackers can exploit this remotely if they can trigger file copy operations, increasing the threat surface. The absence of known exploits in the wild provides a window for proactive mitigation, but the high CVSS score underscores the urgency of addressing this issue.

European organizations should immediately assess their use of OpenZFS versions up to 2.1.13 and 2.2.x through 2.2.1 and plan for prompt upgrades to versions beyond 2.2.1 where the issue is less prevalent or fully patched once available. Until patches are applied, organizations should implement strict integrity verification of critical configuration and security files after any copy or backup operations, using cryptographic hashes or file integrity monitoring tools. Avoid relying solely on OpenZFS's efficient copy mechanisms for security-sensitive files; instead, use verified copy methods that ensure data correctness. Review and harden file copy workflows, especially those involving GNU coreutils cp or similar utilities, to detect and prevent zero-byte file replacements. Employ monitoring and alerting on unexpected changes to critical files like /etc/hosts.deny or access control lists. Limit network exposure of systems running vulnerable OpenZFS versions and restrict access to trusted users only. Finally, maintain up-to-date backups and test restoration procedures to recover from potential silent data corruption incidents.