CVE-2016-8494 in Connect
Summary
by MITRE
Insufficient verification of uploaded files allows attackers with webui administrators privileges to perform arbitrary code execution by uploading a new webui theme.
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Analysis
by VulDB Data Team • 09/01/2020
This vulnerability resides in the webui component of a system where administrators possess the ability to upload custom themes, creating a critical security flaw that enables arbitrary code execution. The issue stems from inadequate validation mechanisms during the file upload process, specifically within the theme upload functionality that lacks proper sanitization and verification protocols. Attackers with administrative webui privileges can exploit this weakness by crafting malicious theme files that contain executable code, bypassing normal security restrictions that should prevent such uploads. The vulnerability represents a classic path to privilege escalation and remote code execution, as it allows authenticated users to execute arbitrary commands on the target system with the privileges of the webui service account.
The technical implementation of this flaw involves the webui's theme upload handler failing to properly validate file types, content, or execution permissions associated with uploaded theme components. When administrators upload theme files, the system should verify that these files conform to expected formats and do not contain malicious code or executable elements. However, the insufficient verification allows attackers to upload files with extensions that appear legitimate but contain hidden malicious payloads or scripts that execute when the theme is processed or rendered. This type of vulnerability aligns with CWE-434 which describes insecure upload of executable code, and represents a significant gap in the application's input validation and file handling security controls.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with persistent access to the system and potentially allows for further exploitation within the network. Once an attacker successfully uploads a malicious theme, they can execute commands with the privileges of the webui service, potentially leading to complete system compromise. The vulnerability is particularly dangerous because it requires only webui administrative privileges, which are often less restricted than full system administrator access, making it easier for attackers to gain a foothold. This weakness can enable attackers to establish backdoors, exfiltrate data, or use the compromised system as a launch point for further attacks against other network resources.
Mitigation strategies for this vulnerability should focus on implementing robust file validation and sanitization mechanisms within the upload process. Organizations should enforce strict file type validation, reject executable file extensions, and implement content analysis to detect potentially malicious code within uploaded files. The system should also employ proper file handling practices such as storing uploaded files in non-executable directories and implementing proper access controls for uploaded content. Additionally, the principle of least privilege should be enforced by ensuring that webui administrators have minimal necessary permissions and that uploaded themes are processed in sandboxed environments. This vulnerability demonstrates the critical importance of secure file upload handling and aligns with ATT&CK technique T1059 for command and scripting interpreter, as it enables attackers to execute arbitrary code through the compromised upload mechanism. Organizations should also implement regular security testing including file upload vulnerability assessments and maintain up-to-date security patches to prevent exploitation of such weaknesses.