CVE-2024-45511 is a reflected Cross-Site Scripting (XSS) vulnerability affecting Zimbra Collaboration Suite (ZCS) through version 10.1, specifically within the Briefcase module that integrates OnlyOffice for document formatting. The vulnerability stems from inadequate sanitization of file content processed by the OnlyOffice formatter. An attacker can upload a maliciously crafted file to a shared folder and then lure a victim into opening a URL referencing this folder. Upon doing so, the malicious JavaScript embedded in the file executes in the context of the victim's browser session, potentially allowing the attacker to hijack the session, steal cookies, or perform actions on behalf of the victim. The attack requires the victim to have at least limited privileges (PR:L) and to interact with the malicious URL (UI:R). The vulnerability impacts confidentiality and integrity but not availability, as it does not cause denial of service. The CVSS 3.1 base score is 6.1, reflecting medium severity with network attack vector, low attack complexity, and scope change. No public exploits are currently known, but the vulnerability is publicly disclosed and should be addressed promptly. The issue is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation).

The primary impact of this vulnerability is the potential compromise of user session confidentiality and integrity within Zimbra Collaboration environments. Successful exploitation could allow attackers to execute arbitrary JavaScript in the victim's browser, leading to session hijacking, theft of sensitive information such as authentication tokens or cookies, and unauthorized actions performed with the victim's privileges. This can facilitate further lateral movement or privilege escalation within an organization. While the vulnerability does not directly affect system availability, the indirect consequences of compromised accounts or data leakage can be severe, including data breaches and loss of trust. Organizations relying on Zimbra Collaboration for email and document sharing, especially those using the Briefcase module with OnlyOffice integration, are at risk. The requirement for user interaction and limited privileges reduces the ease of exploitation but does not eliminate the threat, particularly in targeted phishing or social engineering campaigns.

To mitigate CVE-2024-45511, organizations should first check for and apply any official patches or updates released by Zimbra addressing this vulnerability. If patches are not yet available, administrators should consider disabling the OnlyOffice formatter integration within the Briefcase module or restricting file sharing capabilities to trusted users only. Implementing strict input validation and sanitization on file content before rendering can reduce risk. Additionally, organizations should educate users about the dangers of opening unsolicited or suspicious URLs, especially those pointing to shared folders or documents. Employing web application firewalls (WAFs) with rules to detect and block reflected XSS payloads targeting Zimbra can provide an additional layer of defense. Monitoring logs for unusual access patterns or repeated attempts to access shared folders with malicious files can help detect exploitation attempts early. Finally, enforcing least privilege principles and multi-factor authentication (MFA) can limit the damage if an account is compromised.