CVE-2018-6882 in Zimbra Collaboration
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the ZmMailMsgView.getAttachmentLinkHtml function in Zimbra Collaboration Suite (ZCS) before 8.7 Patch 1 and 8.8.x before 8.8.7 might allow remote attackers to inject arbitrary web script or HTML via a Content-Location header in an email attachment.
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Analysis
by VulDB Data Team • 02/25/2025
The vulnerability CVE-2018-6882 represents a critical cross-site scripting flaw within the Zimbra Collaboration Suite email platform, specifically affecting versions prior to 8.7 Patch 1 and 8.8.x versions before 8.8.7. This vulnerability resides in the ZmMailMsgView.getAttachmentLinkHtml function which processes email attachments and generates HTML content for display within the web interface. The flaw manifests when the system fails to properly sanitize user-supplied data from the Content-Location header of email attachments, creating an avenue for malicious actors to execute arbitrary web scripts or HTML code in the context of a victim's browser session.
The technical exploitation of this vulnerability occurs through the manipulation of email headers, specifically the Content-Location header that is often used to specify the location of an attachment or resource. When Zimbra processes an email containing a maliciously crafted Content-Location header, the getAttachmentLinkHtml function does not adequately filter or escape the input data before incorporating it into the generated HTML output. This failure in input validation and output sanitization creates a classic XSS attack vector where attackers can inject malicious scripts that execute in the context of the authenticated user's browser, potentially leading to session hijacking, credential theft, or other malicious activities.
The operational impact of this vulnerability extends beyond simple script injection as it represents a significant threat to email security and user privacy within enterprise environments that rely on Zimbra for their communication infrastructure. Attackers can leverage this flaw to craft phishing emails that appear legitimate while simultaneously executing malicious code, potentially bypassing traditional email security measures that focus on content inspection rather than header manipulation. The vulnerability affects the web-based interface of Zimbra, meaning that any authenticated user who views an affected email attachment could be compromised, making it particularly dangerous in corporate settings where users frequently interact with email content. According to CWE-79, this vulnerability maps directly to Cross-site Scripting, while the ATT&CK framework categorizes this under T1566 - Phishing and T1059 - Command and Scripting Interpreter, highlighting both the initial access vector and execution methods.
Organizations utilizing Zimbra Collaboration Suite must implement immediate remediation measures including upgrading to the patched versions 8.7 Patch 1 or 8.8.7 and higher, as well as implementing additional security controls such as email header filtering and content security policies. The vulnerability demonstrates the importance of proper input validation and output encoding in web applications, particularly when dealing with user-supplied data from email headers. Security teams should also consider implementing web application firewalls and monitoring for suspicious email header patterns to detect potential exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to ensure that all components of the email infrastructure remain protected against similar classes of vulnerabilities, as this flaw exemplifies the ongoing challenge of securing email systems against sophisticated attack vectors that exploit seemingly benign email metadata fields.