CVE-2024-50599 identifies a reflected Cross-Site Scripting (XSS) vulnerability in the Zimbra Collaboration Suite (ZCS) version 8.8.15, specifically targeting one of its webmail calendar endpoints. Reflected XSS occurs when an application takes user input and immediately includes it in the response HTML without proper sanitization or encoding, enabling attackers to inject malicious JavaScript code. In this case, the vulnerability arises due to improper handling of user-supplied input parameters in the calendar functionality, which are reflected back in the web interface. An attacker can craft a malicious URL containing a payload that, when clicked by a victim, executes arbitrary scripts in the victim's browser context. This can lead to theft of session cookies, redirection to phishing sites, or unauthorized actions performed on behalf of the user. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) indicates the attack can be launched remotely over the network with low complexity, requires no privileges, but does require user interaction (clicking a link). The scope is changed, meaning the vulnerability affects resources beyond the vulnerable component, and the impact is limited to partial loss of confidentiality and integrity without affecting availability. No patches or exploits are currently publicly available, but the vulnerability is publicly disclosed as of November 7, 2024. The CWE-79 classification confirms this is a classic XSS flaw. Given Zimbra's widespread use in enterprise and government email and collaboration environments, this vulnerability poses a significant risk if exploited.

The primary impact of CVE-2024-50599 is the potential compromise of user confidentiality and integrity within affected Zimbra Collaboration Suite environments. Successful exploitation allows attackers to execute arbitrary scripts in the context of the victim's browser session, potentially leading to session hijacking, credential theft, or unauthorized actions such as sending emails or modifying calendar events. This can facilitate phishing campaigns, lateral movement within networks, or data exfiltration. Although availability is not directly impacted, the indirect consequences of compromised accounts can disrupt organizational operations and trust. Organizations relying on ZCS 8.8.15 for email and calendar services, especially those with sensitive or regulated data, face increased risk of targeted attacks. The requirement for user interaction limits mass exploitation but does not eliminate risk, particularly in environments where social engineering is effective. The vulnerability's network accessibility and low attack complexity make it attractive for attackers aiming to compromise user accounts or gain footholds in enterprise environments.

To mitigate CVE-2024-50599, organizations should: 1) Monitor Zimbra vendor communications closely and apply official patches or updates as soon as they become available. 2) Implement strict input validation and output encoding on all user-supplied data in the webmail calendar endpoints to prevent script injection. 3) Deploy Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. 4) Educate users about the risks of clicking suspicious links, especially those received via email or instant messaging. 5) Use web application firewalls (WAFs) with rules designed to detect and block reflected XSS payloads targeting Zimbra endpoints. 6) Conduct regular security assessments and penetration testing focused on web application vulnerabilities. 7) Monitor logs for unusual activity indicative of attempted XSS exploitation, such as unexpected URL parameters or script execution attempts. 8) Consider isolating or restricting access to the affected calendar functionality if immediate patching is not feasible. These measures, combined, reduce the likelihood and impact of exploitation until a vendor patch is applied.