CVE-2026-4111 is a vulnerability identified in the RAR5 archive decompression logic within the libarchive library, specifically in the archive_read_data() function path used by Red Hat Enterprise Linux 10. When processing a specially crafted RAR5 archive, the decompression routine encounters a logical flaw that causes it to enter an infinite loop. This infinite loop results from an unreachable exit condition in the decompression logic, which prevents forward progress and causes continuous CPU consumption. Because the malicious archive passes checksum validation and appears structurally valid, applications using libarchive cannot detect the problem prior to processing the archive. This vulnerability can be exploited remotely without requiring authentication or user interaction, as it targets automated archive processing services. The consequence is a denial-of-service condition due to resource exhaustion, impacting system availability. The CVSS v3.1 score of 7.5 reflects the high severity of this vulnerability, emphasizing its potential to disrupt services. No known exploits have been reported in the wild as of the publication date. The vulnerability affects Red Hat Enterprise Linux 10 systems that utilize libarchive for RAR5 decompression, which is common in environments that handle compressed archives automatically, such as mail servers, file upload services, or backup systems.

The primary impact of CVE-2026-4111 is a denial-of-service condition caused by an infinite loop during RAR5 archive decompression. This can lead to high CPU utilization, potentially degrading system performance or causing service outages. Organizations that automatically process RAR5 archives—such as email gateways scanning attachments, file upload services, or automated backup and extraction systems—are at risk of service disruption. The vulnerability does not compromise confidentiality or integrity but can severely affect availability, especially in high-throughput or critical environments. Persistent DoS conditions may require manual intervention or system restarts, increasing operational costs and downtime. Additionally, attackers could leverage this flaw to target specific services or infrastructure components, potentially impacting business continuity. Since no authentication or user interaction is required, the attack surface is broad, allowing remote attackers to exploit the vulnerability by submitting crafted archives. This elevates the risk for organizations exposed to untrusted archive files.

To mitigate CVE-2026-4111, organizations should: 1) Apply patches or updates from Red Hat as soon as they become available to fix the libarchive decompression logic. 2) Implement resource limits (e.g., CPU and memory quotas) on processes that handle archive decompression to contain potential infinite loops and prevent system-wide impact. 3) Employ input validation and filtering to block or quarantine suspicious RAR5 archives before processing, possibly using sandboxed environments for decompression. 4) Monitor system resource usage and set alerts for unusual CPU spikes related to archive processing services. 5) Consider disabling automatic processing of RAR5 archives if not strictly necessary or replacing libarchive with alternative libraries that do not exhibit this vulnerability. 6) Maintain strict network controls and limit exposure of services that automatically process archives to trusted sources only. 7) Conduct regular security assessments and update incident response plans to address potential denial-of-service scenarios related to archive processing.