The vulnerability CVE-2026-11839 in Başarsoft Rotaban (version V2026.06.002) is an unrestricted file upload issue (CWE-434) that permits attackers with limited privileges to upload malicious files such as web shells to the server. This can lead to complete compromise of confidentiality, integrity, and availability of the affected system. The vulnerability is fixed starting from version V2026.06.003. No known exploits in the wild have been reported as of the publication date.

Successful exploitation allows an attacker to upload and execute arbitrary code on the web server, leading to full system compromise including data theft, modification, or destruction, and potential disruption of service. The CVSS 3.1 score of 9.9 reflects critical impact on confidentiality, integrity, and availability with network attack vector and low complexity.

Upgrade the affected product from version V2026.06.002 to V2026.06.003 or later, where this vulnerability is fixed. No official patch link is provided, but the vendor has addressed the issue in the subsequent release. Until the upgrade is applied, restrict file upload permissions and monitor for suspicious file uploads if possible.