CVE-2026-11839 -- CVSS 9.9 Vulnerability Briefing

CVE-2026-11839 | CVSS 9.9 (Critical) | Exploit: No known exploit

What Is It

CVE-2026-11839 is an unrestricted file upload vulnerability in Rotaban, a web application developed by Başarsoft Information Technologies Inc., affecting versions from V2026.06.0 onward, which allows an attacker to upload and execute arbitrary web shell files on the server.

Technical Detail

The flaw exists in Rotaban's file upload functionality, which fails to properly validate or restrict the types of files that can be submitted by a user, permitting the upload of server-executable file types such as PHP, ASP, or JSP web shells. An attacker who can reach the upload endpoint submits a malicious file disguised or directly typed as a dangerous server-side script, which is then stored and accessible on the web server. Successful exploitation results in remote code execution (RCE) under the privileges of the web server process, granting the attacker persistent access, lateral movement capability, and full control over hosted data and server resources.

Exploitation Status

No known exploit code has been publicly observed or confirmed at this time. The vulnerability is not currently listed in CISA's Known Exploited Vulnerabilities (KEV) catalog. Despite the absence of confirmed exploitation, the CVSS score of 9.9 (Critical) and the straightforward nature of web shell upload attacks mean that exploitation requires minimal technical sophistication once an attacker identifies a reachable upload endpoint.

Who Is Targeting This

No specific threat actor attribution at this time. Neither confirmed nor reported threat actor associations have been identified in connection with this vulnerability as of June 18, 2026.

What To Do

Organizations running Rotaban versions from V2026.06.0 should contact Başarsoft Information Technologies Inc. immediately to obtain a patched release or vendor-issued guidance, as no specific patch version has been publicly confirmed in available data. As an interim measure, restrict access to file upload functionality to authenticated and authorized users only, enforce strict server-side file type validation using allowlists rather than blocklists, and configure the web server to deny execution permissions on all upload directories. Monitor web server logs for unexpected file creation events in upload paths and for outbound connections originating from web server processes, which may indicate post-exploitation activity. Given the critical severity rating, this should be treated as a high-priority remediation item regardless of the current absence of known active exploitation.