CVE-2021-21247 in OneDev
Summary
by MITRE • 01/16/2021
OneDev is an all-in-one devops platform. In OneDev before version 4.0.3, the application's BasePage registers an AJAX event listener (`AbstractPostAjaxBehavior`) in all pages other than the login page. This listener decodes and deserializes the `data` query parameter. We can access this listener by submitting a POST request to any page. This issue may lead to `post-auth RCE` This endpoint is subject to authentication and, therefore, requires a valid user to carry on the attack. This issue was addressed in 4.0.3 by encrypting serialization payload with secrets only known to server.
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Analysis
by VulDB Data Team • 02/15/2021
The vulnerability CVE-2021-21247 affects OneDev, an all-in-one DevOps platform, and represents a significant security flaw that could enable remote code execution when exploited by authenticated users. This vulnerability exists in versions prior to 4.0.3 and stems from the application's improper handling of serialized data within its web framework. The core issue lies in how the BasePage component registers an AJAX event listener known as AbstractPostAjaxBehavior across virtually all pages of the application, with the notable exception of the login page. This listener is designed to process incoming data through a query parameter named 'data', which is then decoded and deserialized by the application's processing logic. The registration of this event listener creates a persistent attack surface that remains active throughout the user session, regardless of the page being accessed.
The technical implementation of this vulnerability involves the application's deserialization mechanism being exposed through the AJAX endpoint, which accepts POST requests to any page within the application. When a user submits a POST request containing malicious serialized data in the 'data' parameter, the application's BasePage component processes this input through the registered AbstractPostAjaxBehavior listener. This processing flow creates a dangerous deserialization vulnerability that allows an attacker to inject malicious code into the application's execution environment. The vulnerability specifically targets the application's object deserialization routines, which are commonly exploited in server-side request forgery and remote code execution attacks. According to CWE classification, this vulnerability aligns with CWE-502 which covers Deserialization of Untrusted Data, and it represents a classic example of how improper input validation can lead to severe remote execution capabilities.
The operational impact of this vulnerability is particularly concerning because it requires only authentication to exploit, meaning that any authenticated user with valid credentials can potentially execute arbitrary code on the server. This post-authentication RCE capability transforms what might otherwise be a limited privilege escalation into a full system compromise, as the attacker can leverage the application's privileges to execute commands with the same permissions as the application itself. The vulnerability's exploitation path involves crafting malicious serialized payloads that, when processed by the vulnerable deserialization logic, can trigger code execution on the server. Attackers could potentially use this vulnerability to gain access to sensitive data, modify application behavior, install backdoors, or use the compromised system as a pivot point for further attacks within the network infrastructure. The fact that this vulnerability affects all pages except the login page means that the attack surface is extensive and difficult to fully mitigate without patching the core application components.
The security implications extend beyond simple code execution to include potential data breaches and system compromise. Once an attacker successfully exploits this vulnerability, they could access the underlying database, manipulate application data, or even escalate privileges to system-level access depending on how the application is configured and deployed. The vulnerability's persistence across multiple pages means that attackers have numerous opportunities to trigger the exploit, making detection and prevention more challenging. From an ATT&CK framework perspective, this vulnerability maps to techniques involving deserialization attacks and privilege escalation, with potential lateral movement capabilities once the initial compromise is achieved. The fix implemented in version 4.0.3 addresses the core issue by encrypting serialization payloads with server-side secrets that are unknown to potential attackers, effectively preventing the malicious deserialization process from succeeding. This mitigation strategy aligns with defense-in-depth principles and demonstrates the importance of proper input validation and secure deserialization practices in web applications. Organizations using OneDev should prioritize immediate patching to protect against this vulnerability, as the combination of authentication requirement with remote code execution potential makes it a critical security concern that could lead to complete system compromise if left unaddressed.