An issue was discovered in Zimbra Collaboration (ZCS) versions 9.0, 10.0, and 10.1. This vulnerability allows an attacker to execute arbitrary JavaScript within the victim's session due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail containing a malicious ICS entry, the embedded JavaScript executes via an ontoggle event inside a <details> tag. Consequently, attackers may leverage this vulnerability to perform unauthorized actions, such as redirecting emails to an attacker-controlled address or exfiltrating sensitive data.
The severity of this vulnerability is classified as medium with a CVSS score of 5.4. Organizations utilizing affected versions of Zimbra Collaboration Suite should recognize the potential risks involved. The execution of arbitrary JavaScript can lead to significant security implications, including unauthorized access to user accounts and data manipulation.
With confirmed exploitation status in the Known Exploited Vulnerabilities (KEV) catalog, security teams must take action. Organizations should prioritize patching immediately to mitigate risks associated with this vulnerability.
The details of this vulnerability were published on March 12, 2025, and require urgent attention from security teams to safeguard against potential exploitation.
Vulnerability Details
The vulnerability is classified as a stored cross-site scripting (XSS) flaw, identified by CWE-79. The CVSS score of 5.4 indicates a medium severity level, which necessitates timely remediation.
Affected versions include Zimbra Collaboration Suite 9.0, 10.0, and 10.1. This vulnerability was disclosed on March 12, 2025.
Technical Analysis
The root cause of this vulnerability stems from improper sanitization of HTML content when processing ICS files. Attackers can exploit this by crafting malicious ICS files that execute JavaScript when opened.
The attack vector is network-based, requiring low complexity to exploit. It necessitates low privileges and user interaction, as the victim must view the email with the malicious ICS file.
The impacts include low confidentiality and integrity, while availability remains unaffected by this vulnerability.
Risk & Impact Analysis
Risk to organizations includes potential unauthorized access to user accounts, leading to email redirection and data exfiltration. Given the medium severity rating, organizations should address this vulnerability in their priority patch cycle to minimize exploitation risks.
The blast radius of this vulnerability can extend to all users of affected Zimbra Collaboration Suite versions, highlighting the urgent need for remediation.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | No |
Actively Exploited | Yes |
Ransomware Use | No |
Affected Versions
The vulnerable versions of Zimbra Collaboration Suite include 9.0.0 and all versions prior to 10.0.13 and 10.1.0 to 10.1.5. Organizations should ensure they are running patched versions to mitigate this vulnerability.
Mitigation & Remediation
Organizations should apply available patches and updates from Synacor to remediate this vulnerability. If a patch is not available, consider implementing network controls to limit access to vulnerable components and monitor for unusual activity indicative of exploitation.
For further information on how to secure your environment, organizations can benefit from comprehensive penetration testing services that identify weaknesses in their security posture.
Detection Guidance
Organizations should monitor email logs for unexpected ICS file attachments and analyze user account activity for unauthorized email forwarding rules. Behavioral anomalies such as unexpected changes in user account settings may also indicate exploitation.
AppSecure Threat Intelligence Insight
The emergence of this cross-site scripting vulnerability in widely used collaboration software highlights the importance of rigorous input sanitization practices. Security teams should take note of the increasing trend of exploiting such vulnerabilities in communication platforms.
To learn more about best practices for securing applications, consider reviewing our penetration testing methodology and explore how proactive security measures can prevent similar vulnerabilities in the future.
Organizations are encouraged to stay informed about emerging threats and to adapt their security strategies accordingly. For those using cloud services, it's critical to follow applicable guidance, such as BOD 22-01, to mitigate risks associated with vulnerabilities like this.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
.webp)