Horizon Alert
Summary of the vulnerability and why it matters
Zimbra Collaboration Suite (ZCS) Classic UI is susceptible to a stored cross-site scripting vulnerability. This flaw allows attackers to inject malicious code through Cascading Style Sheets (CSS) @import directives within HTML email messages. The exploitation of this vulnerability can lead to unauthorized data access and manipulation within the affected systems, posing a risk to organizational data integrity and user privacy.
- Vulnerable component: Zimbra Collaboration Suite Classic UI.
- Core weakness: CSS @import directive injection in HTML emails.
- Main business impact: Unauthorized data access and manipulation.
Attack Path
How an attacker could exploit the issue
An attacker can exploit a stored cross-site scripting vulnerability within the Zimbra Collaboration Suite. This vulnerability arises from the improper handling of Cascading Style Sheets (CSS) @import directives within HTML email messages. Exploitation allows attackers to inject malicious scripts that execute within the context of a user's browser session, potentially leading to unauthorized access or data manipulation. The attack is initiated when a user opens a specially crafted email.
- Emails containing malicious CSS can be sent.
- Attackers trigger script execution.
- Control over user sessions is gained.
Live Threat
Current exploitation, exposure, and threat context
This vulnerability affects Zimbra Collaboration Suite by allowing attackers to inject malicious code through specially crafted emails. This could potentially lead to unauthorized access to user data or the disruption of services. Organizations utilizing this software should consider this a significant risk due to the potential for widespread impact.
- Likely attacker skill level: Low
- Required access or conditions: User must open a crafted email
- Business risk or urgency: High
Priority actions
Operational Fix
Recommended remediation, mitigation, and detection steps
This vulnerability impacts organizations using Zimbra Collaboration Suite (ZCS) through stored cross-site scripting in the Classic UI. Attackers can exploit this by sending specially crafted HTML emails that include CSS @import directives. This could lead to unauthorized access to sensitive data or the execution of malicious scripts within the affected user's browser session, posing a business risk to data confidentiality and integrity.
- Find affected Zimbra Collaboration Suite assets.
- Reduce exposure or isolate affected systems.
- Apply vendor fix, verify, and monitor.
