CVE-2021-35207 in Zimbra Collaboration Suite
Summary
by MITRE • 07/03/2021
An issue was discovered in Zimbra Collaboration Suite 8.8 before 8.8.15 Patch 23 and 9.0 before 9.0.0 Patch 16. An XSS vulnerability exists in the login component of Zimbra Web Client, in which an attacker can execute arbitrary JavaScript by adding executable JavaScript to the loginErrorCode parameter of the login url.
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Analysis
by VulDB Data Team • 07/09/2021
The vulnerability identified as CVE-2021-35207 represents a critical cross-site scripting flaw within the Zimbra Collaboration Suite web client interface. This security weakness affects versions prior to the specified patch releases, specifically impacting Zimbra 8.8 before 8.8.15 Patch 23 and 9.0 before 9.0.0 Patch 16. The vulnerability resides within the login component of the Zimbra Web Client where user input is not properly sanitized before being rendered back to the browser. The flaw manifests when an attacker manipulates the loginErrorCode parameter in the login URL, allowing them to inject malicious JavaScript code that executes in the context of authenticated users' browsers.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding practices within the Zimbra web application's authentication flow. When the system processes the loginErrorCode parameter, it fails to properly escape or validate the input data before incorporating it into the HTML response. This allows an attacker to craft malicious URLs containing JavaScript payloads that are executed when the vulnerable page renders. The vulnerability is classified under CWE-79 as a cross-site scripting weakness, specifically demonstrating the dangerous combination of unsanitized user input being directly embedded into web page content without proper context-specific escaping.
The operational impact of this vulnerability extends beyond simple script execution, creating a potential attack vector for more sophisticated exploits. An attacker could leverage this XSS flaw to steal session cookies, perform unauthorized actions on behalf of authenticated users, or redirect victims to malicious sites. The attack requires minimal user interaction since the vulnerability is present in the login component, making it particularly dangerous as users naturally visit the login page when accessing the service. This vulnerability aligns with ATT&CK technique T1531 which describes the use of malicious inputs to gain access to systems through web application vulnerabilities.
The security implications of this vulnerability are particularly severe given that it affects the core authentication mechanism of the Zimbra collaboration platform. Since the login page is frequently accessed by users, the attack surface is extensive and the potential for successful exploitation is high. Organizations using affected versions of Zimbra face significant risk of credential theft, unauthorized access to email accounts, and potential data breaches. The vulnerability demonstrates poor input sanitization practices and highlights the importance of implementing robust security controls around all user-provided data, especially in authentication-related components where the consequences of exploitation can be catastrophic for enterprise security. The recommended mitigation involves applying the vendor-provided patches to update to versions 8.8.15 Patch 23 or 9.0.0 Patch 16, which contain the necessary fixes to properly sanitize the loginErrorCode parameter and prevent malicious JavaScript execution.