CVE-2024-33536 in Zimbra Collaboration Suite
Summary
by MITRE • 08/12/2024
An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0. The vulnerability occurs due to inadequate input validation of the res parameter, allowing an authenticated attacker to inject and execute arbitrary JavaScript code within the context of another user's browser session. By uploading a malicious JavaScript file, accessible externally, and crafting a URL containing its location in the res parameter, the attacker can exploit this vulnerability. Subsequently, when another user visits the crafted URL, the malicious JavaScript code is executed.
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Analysis
by VulDB Data Team • 03/15/2025
This vulnerability exists within Zimbra Collaboration Suite versions 9.0 and 10.0, representing a critical cross-site scripting flaw that enables authenticated attackers to perform persistent code execution against other users. The vulnerability stems from insufficient input validation of the res parameter in the application's handling of resource references, creating a pathway for malicious code injection that operates within the context of legitimate user sessions. The flaw allows an attacker with valid credentials to upload malicious JavaScript content to the system's external accessible storage, then craft specially formatted URLs that include the malicious resource location within the res parameter. When other users access these crafted URLs, the embedded JavaScript executes in their browser sessions, potentially enabling session hijacking, data theft, or further exploitation. This vulnerability directly maps to CWE-79 - Improper Neutralization of Input During Web Page Generation, which is a fundamental web application security weakness that has been classified under the OWASP Top Ten as a critical risk factor. The attack vector operates through the principle of stored cross-site scripting where the malicious code is stored on the server and executed when other users access the affected application components. The impact extends beyond simple script execution as it enables attackers to manipulate user sessions, potentially gaining unauthorized access to sensitive email communications, calendar data, and contact information. The vulnerability's exploitation requires only basic authentication access to the system, making it particularly dangerous as it can be leveraged by insiders or compromised accounts. The persistent nature of this flaw means that once exploited, the malicious code continues to execute for any user who visits the crafted URL, creating a sustained attack vector that can be difficult to detect and remediate. This type of vulnerability is categorized under the ATT&CK framework as T1059.007 - Command and Scripting Interpreter: JavaScript, and more specifically T1566.002 - Phishing: Spearphishing Attachment, as the attack typically involves tricking users into visiting malicious URLs. The security implications are severe as Zimbra serves as an enterprise email and collaboration platform where users often have access to sensitive business data and communications. Organizations relying on these versions of Zimbra face significant risk of data breaches, privilege escalation, and potential lateral movement within their networks. The vulnerability demonstrates a critical failure in input sanitization and output encoding practices that should be implemented at multiple layers of the application stack to prevent such injection attacks. The flaw's exploitation mechanism aligns with common attack patterns found in web application security where parameter manipulation leads to unauthorized code execution, making it a prime target for automated exploitation tools and advanced persistent threat actors.
The technical implementation of this vulnerability exploits the application's trust in user-supplied input without proper validation or sanitization of the res parameter. When Zimbra processes requests containing this parameter, it fails to properly escape or validate the input before incorporating it into web page content, allowing the attacker to inject malicious JavaScript code that executes in the victim's browser context. The attack requires the attacker to first establish access to the system's file upload functionality, which then enables them to place malicious content in a location accessible through external URLs. The crafted URL construction process involves embedding the malicious resource path within the res parameter, which is then processed by the application's resource handling logic without adequate security controls. This creates a persistent XSS vulnerability that can be triggered by any user who accesses the malicious URL, regardless of their authentication state or privileges within the system. The vulnerability's severity is amplified by the fact that it operates at the application layer where user sessions are maintained, allowing for session manipulation and potential privilege escalation. The flaw represents a failure in the application's security architecture and demonstrates the importance of implementing defense-in-depth strategies that include input validation, output encoding, and secure coding practices. The vulnerability's existence in both major versions of Zimbra (9.0 and 10.0) indicates a systemic issue in the application's security controls that requires immediate remediation through patching or implementing compensating controls.
Mitigation strategies for this vulnerability should include immediate deployment of vendor-provided patches or updates that address the input validation flaw in the res parameter handling. Organizations should implement network-level controls such as web application firewalls that can detect and block malicious URL patterns targeting this specific vulnerability. The implementation of Content Security Policy headers can help prevent execution of unauthorized scripts even if the vulnerability is exploited. Additionally, administrators should conduct regular security assessments to identify other potential injection points in the application and implement proper input sanitization and output encoding for all user-supplied data. User education and awareness programs should emphasize the importance of not clicking on suspicious links or visiting untrusted URLs, particularly when accessing enterprise collaboration platforms. The vulnerability's exploitation requires authentication, so implementing strong access controls and monitoring for unusual upload activities can help detect potential attacks. Organizations should also consider implementing automated monitoring systems that can detect the presence of malicious JavaScript code in uploaded files or resource references. Regular security audits of web application configurations and input validation mechanisms should be conducted to ensure that similar vulnerabilities do not exist in other parts of the system. The remediation approach should align with security frameworks such as NIST SP 800-53 controls for input validation and output encoding, ensuring that the fix addresses the root cause rather than just the symptoms. Implementing principle of least privilege access controls for file upload functionality can limit the damage potential if the vulnerability is exploited, while regular security testing including penetration testing and vulnerability scanning should be performed to validate the effectiveness of implemented controls.