CVE-2026-3748 in Bytedesk
Summary
by MITRE • 03/08/2026
A security flaw has been discovered in Bytedesk up to 1.3.9. This affects the function uploadFile of the file source-code/src/main/java/com/bytedesk/core/upload/UploadRestController.java of the component SVG File Handler. Performing a manipulation results in unrestricted upload. Remote exploitation of the attack is possible. The exploit has been released to the public and may be used for attacks. Upgrading to version 1.4.5.1 is able to mitigate this issue. The patch is named 975e39e4dd527596987559f56c5f9f973f64eff7. Upgrading the affected component is recommended.
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Analysis
by VulDB Data Team • 03/12/2026
The vulnerability identified as CVE-2026-3748 represents a critical security flaw in Bytedesk version 1.3.9 and earlier, specifically within the file upload functionality of the SVG File Handler component. This issue resides in the uploadFile function located at file source-code/src/main/java/com/bytedesk/core/upload/UploadRestController.java, where inadequate input validation and sanitization mechanisms fail to properly restrict file uploads. The flaw allows attackers to bypass normal upload restrictions and execute unrestricted file uploads, creating a significant vector for potential exploitation.
The technical implementation of this vulnerability stems from insufficient validation of uploaded file types and content within the SVG File Handler module. When users attempt to upload files through the designated upload endpoint, the system fails to properly verify the file extension, MIME type, or content structure before processing the upload. This lack of proper validation creates an unrestricted upload condition that directly maps to CWE-434, which specifically addresses the improper restriction of uploads of executable files. The vulnerability's design flaw allows malicious actors to upload potentially harmful files including web shells, malicious scripts, or other exploit payloads that could compromise the entire system.
Remote exploitation of this vulnerability is fully feasible and has been documented as having public exploit code available, significantly increasing the threat level. Attackers can leverage this weakness to upload malicious files directly to the target system without requiring local access or physical presence. The implications extend beyond simple file upload capabilities, as the unrestricted nature of the vulnerability allows for arbitrary code execution and potential system compromise. This vulnerability aligns with ATT&CK technique T1195.001, which covers the use of malicious files for initial access and persistence within compromised systems. The attack surface is particularly concerning given that the vulnerability affects a core file handling component that likely processes user-uploaded content for various applications and services.
The operational impact of CVE-2026-3748 is substantial, as successful exploitation could lead to complete system compromise, data theft, or service disruption. Organizations utilizing Bytedesk versions prior to 1.4.5.1 face significant risk of unauthorized access, privilege escalation, and potential lateral movement within their network infrastructure. The unrestricted upload capability provides attackers with a direct pathway to establish persistent access and execute malicious code with the privileges of the web application. Additionally, the presence of public exploit code means that this vulnerability is likely to be actively exploited by threat actors without requiring advanced technical skills, making it particularly dangerous in production environments.
The recommended mitigation strategy involves immediate upgrading to Bytedesk version 1.4.5.1, which includes the patch identified by commit hash 975e39e4dd527596987559f56c5f9f973f64eff7. This upgrade addresses the core validation issues within the SVG File Handler component and implements proper file type restrictions and content verification mechanisms. Organizations should also implement additional defensive measures such as restricting upload permissions, implementing file content scanning, and monitoring upload activities for suspicious patterns. The patch resolution specifically targets the CWE-434 vulnerability by enforcing proper file validation and ensuring that only approved file types are accepted for processing within the upload functionality.