CVE-2026-39757 in Taskbot Plugin
Summary
by MITRE • 10/06/2026
Subscriber Arbitrary File Upload in Taskbot <= 6.6 versions.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified as an arbitrary file upload flaw within Taskbot versions prior to or equal to 6.6 represents a critical security deficiency that allows unauthenticated or low-privileged users to bypass intended access controls and execute malicious code on the target server. This type of vulnerability typically arises from inadequate validation, sanitization, and verification mechanisms when handling user-supplied file inputs. In the context of Taskbot, which is often utilized for workflow automation and task management, the ability to upload arbitrary files can have severe consequences depending on how the uploaded content is processed by the underlying system or web server infrastructure.
From a technical perspective, this flaw likely stems from insufficient checks regarding file extensions, MIME types, or content inspection during the upload process. Attackers may exploit this weakness by crafting requests that include malicious payloads disguised as legitimate files, such as PHP scripts, JSP shells, or other executable formats supported by the server environment. If the application fails to strictly enforce allowlists for permitted file types and does not properly sanitize filenames to prevent directory traversal attacks, an attacker can upload a web shell directly into a publicly accessible directory. This effectively grants the attacker remote code execution capabilities on the compromised host.
The operational impact of this vulnerability is profound, as it serves as a direct pathway to full system compromise. Once a malicious file is successfully uploaded and executed, attackers can escalate privileges, exfiltrate sensitive data stored within the Taskbot database or associated systems, install additional malware such as ransomware or cryptominers, and use the compromised server as a pivot point for further attacks against internal network resources. This aligns with common attack patterns described in industry standards, specifically mapping to CWE-434: Unrestricted Upload of File with Dangerous Type and CWE-79: Improper Neutralization of Input During Web Page Generation if cross-site scripting vectors are also involved due to poor filename handling. Furthermore, the exploitation technique corresponds to MITRE ATT&CK techniques such as T1505.002 (Web Shell) under the Persistence tactic, allowing attackers to maintain long-term access and control over the affected environment.
Mitigation strategies must prioritize immediate patching of Taskbot to version 6.7 or later where these issues have been addressed by the vendor. In cases where upgrading is not immediately feasible, administrators should implement strict input validation on the server side, ensuring that only whitelisted file extensions are accepted and that uploaded files are stored in non-executable directories with restrictive permissions. Additionally, deploying a Web Application Firewall can help detect and block known upload-based attack patterns, while regular security audits and penetration testing should be conducted to identify similar weaknesses across other components of the application ecosystem.