CVE-2023-39804 is a vulnerability identified in GNU tar versions before 1.35, specifically related to the handling of extension attributes within PAX archive files. The vulnerability is located in the xheader.c source file, where malformed or maliciously crafted PAX headers cause the application to mishandle extension attributes, resulting in a crash. This crash leads to a denial-of-service (DoS) condition, disrupting the normal operation of GNU tar when processing such archives. The Common Vulnerability Scoring System (CVSS) score assigned is 6.2 (medium severity), reflecting the fact that the vulnerability affects availability but does not compromise confidentiality or integrity. The attack vector is local (AV:L), meaning an attacker must have local access to the system to exploit the flaw by providing a crafted PAX archive to GNU tar. No privileges are required (PR:N), and no user interaction is necessary (UI:N). The scope remains unchanged (S:U), indicating the impact is confined to the vulnerable component. There are no known exploits in the wild, and no patches or mitigation links were provided in the source data, but the issue is addressed in GNU tar version 1.35 and later. The vulnerability could be exploited by an attacker to cause application crashes during archive extraction or creation, potentially interrupting backup, restore, or deployment processes that rely on GNU tar. This could lead to operational downtime or delays in critical file management tasks. Since GNU tar is widely used in Unix-like environments, including many Linux distributions common in European organizations, the vulnerability has broad relevance. The flaw does not allow code execution or data leakage, limiting its impact to availability disruptions.

The primary impact of CVE-2023-39804 is denial of service through application crashes when processing maliciously crafted PAX archives. For European organizations, this can disrupt automated backup, restore, or deployment workflows that depend on GNU tar, potentially causing operational delays or data availability issues. Organizations with critical infrastructure or services relying on tar for file archiving may experience interruptions affecting business continuity. Although the vulnerability does not compromise confidentiality or integrity, repeated exploitation could degrade system reliability and increase administrative overhead. The requirement for local access limits remote exploitation risk, but insider threats or compromised local accounts could leverage this vulnerability. In environments with high automation and frequent archive handling, such as software development, data centers, and cloud providers, the impact could be more pronounced. European sectors with stringent uptime requirements, including finance, healthcare, and government, may face increased risk from service disruptions. However, the absence of known exploits and the medium severity rating suggest the threat is moderate but warrants timely remediation to prevent potential denial-of-service incidents.

To mitigate CVE-2023-39804, European organizations should prioritize upgrading GNU tar to version 1.35 or later, where the vulnerability is resolved. Until upgrades are applied, restrict the processing of untrusted or unauthenticated PAX archives, especially from local users or automated systems. Implement file integrity monitoring and logging to detect abnormal crashes or unusual tar activity that may indicate exploitation attempts. Employ access controls to limit local user permissions and reduce the risk of malicious archive injection. In automated pipelines, validate and sanitize archive inputs before processing with GNU tar. Consider using alternative archiving tools with robust security postures if immediate patching is not feasible. Regularly review and update system software inventories to ensure vulnerable versions are identified and remediated promptly. Additionally, educate system administrators about this vulnerability to increase awareness and encourage proactive patch management. For critical systems, implement redundancy and failover mechanisms to minimize downtime caused by potential tar crashes.