CVE-2026-93641 in Collaboration Suite
Summary
by MITRE • 09/25/2026
An unauthenticated sender can forge a share notification that triggers stored XSS when a signed-in Zimbra Classic recipient clicks Accept Share, allowing the attacker to access mailbox data and act as the victim.
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Analysis
by VulDB Data Team • 09/25/2026
The vulnerability described constitutes a critical security flaw within the Zimbra Collaboration Suite, specifically affecting the email sharing functionality in the Classic interface. This issue stems from an insufficient validation of input data originating from unauthenticated sources, which allows for the injection of malicious script code into shared content metadata or notifications. The core technical failure lies in the application's inability to properly sanitize user-supplied data before it is processed and subsequently rendered by the recipient's web browser. When a signed-in user receives a share notification that has been forged by an attacker who does not possess valid authentication credentials, the system fails to verify the integrity or origin of the request adequately. This lack of rigorous validation permits the embedding of cross-site scripting payloads within the shared resource metadata, which are then executed when the recipient interacts with the interface.
The operational impact of this vulnerability is severe due to its potential for account takeover and data exfiltration. Once a victim clicks the Accept Share button in their Zimbra Classic client, the malicious script embedded in the forged notification executes within the context of the user's active session. This execution grants the attacker full access to the browser's local storage, cookies, and DOM elements associated with the Zimbra web application. Consequently, an adversary can harvest sensitive authentication tokens, read private emails stored in the victim's mailbox, view contact lists, and potentially perform actions on behalf of the victim such as sending malicious emails or modifying settings. This effectively bypasses the need for direct credential theft through phishing, relying instead on social engineering to trigger the execution of the payload via a seemingly legitimate share notification.
From a classification perspective, this vulnerability aligns with CWE-79: Improper Neutralization of Input During Web Page Generation, commonly known as Cross-Site Scripting (XSS). Specifically, it represents stored XSS because the malicious script is persisted on the server side within the shared resource metadata and retrieved later by multiple users. In terms of offensive security frameworks, this attack vector maps to ATT&CK technique T1059: Command and Scripting Interpreter, where JavaScript serves as the scripting language used for execution. Furthermore, it relates to T1213: Data from Information Repositories, as the primary goal is to extract data from the victim's mailbox, which acts as an information repository within the collaboration suite. The unauthenticated nature of the initial trigger also highlights weaknesses in access control mechanisms regarding how share requests are validated before being processed by authenticated users.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Administrators should apply vendor-provided patches that address this specific flaw as soon as they become available, ensuring that input validation routines are updated to strictly enforce allow-lists for shared content metadata. In the interim, security teams can implement web application firewall rules designed to detect and block common XSS payloads within HTTP requests related to share notifications. Additionally, enabling Content Security Policy headers with strict directives regarding script sources can significantly reduce the impact of any successfully injected scripts by preventing unauthorized execution contexts. User awareness training is also critical; administrators should educate users on verifying the source of unexpected sharing invitations and reporting suspicious activities, thereby reducing the likelihood of successful social engineering attacks that exploit this technical vulnerability.