CVE-2023-45207 in Zimbra Collaboration Suite
Summary
by MITRE • 02/13/2024
An issue was discovered in Zimbra Collaboration (ZCS) 8.8.15, 9.0, and 10.0. An attacker can send a PDF document through mail that contains malicious JavaScript. While previewing this file in webmail in the Chrome browser, the stored XSS payload is executed. (This has been mitigated by sanitising the JavaScript code present in a PDF document.)
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Analysis
by VulDB Data Team • 04/19/2025
The vulnerability CVE-2023-45207 represents a critical cross-site scripting flaw within Zimbra Collaboration Suite versions 8.8.15, 9.0, and 10.0 that specifically targets the webmail interface when processing PDF attachments. This issue arises from insufficient input validation and sanitization mechanisms within the PDF preview functionality, creating an attack vector that leverages the inherent trust users place in email attachments. The vulnerability demonstrates a classic stored XSS scenario where malicious code embedded within a PDF document executes automatically during preview operations, bypassing traditional security boundaries that typically protect against such attacks. The exploitation requires minimal user interaction beyond opening an email containing the malicious attachment, making it particularly dangerous in enterprise environments where email is a primary communication channel.
The technical flaw manifests in how the Zimbra webmail interface handles PDF document previews, specifically when rendered within Chrome browser environments. When users open a PDF attachment through the webmail interface, the system attempts to process and display the document content without adequate sanitization of embedded JavaScript code. This processing occurs at the client-side rendering level, where the browser executes JavaScript code embedded within the PDF file regardless of the document's origin or intended purpose. The vulnerability stems from inadequate content security policies and insufficient filtering of potentially malicious code elements within PDF documents, allowing attackers to embed malicious scripts that execute within the context of the user's authenticated session. The flaw aligns with CWE-79 Cross-site Scripting and demonstrates weaknesses in input validation and output encoding practices.
The operational impact of CVE-2023-45207 extends beyond simple data theft or session hijacking, as it provides attackers with the capability to execute arbitrary commands within the user's browser context. This vulnerability enables attackers to access sensitive email communications, modify user settings, harvest authentication tokens, or redirect users to malicious websites. The attack surface is particularly concerning in enterprise environments where Zimbra serves as the primary email platform, as successful exploitation could lead to lateral movement within the network or compromise of additional user accounts. The vulnerability's effectiveness is amplified by the widespread use of Chrome browsers in corporate email environments, where the browser's JavaScript execution capabilities directly enable the payload delivery. Organizations with limited security awareness training may find this vulnerability particularly dangerous, as users may unknowingly trigger the exploit simply by opening an email message.
Mitigation strategies for CVE-2023-45207 should focus on both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The most effective immediate solution involves applying the vendor-provided security patches that implement proper JavaScript sanitization within PDF preview functionality, aligning with ATT&CK technique T1203 Exploitation for Client Execution. Organizations should also implement additional protective measures such as disabling PDF preview functionality in webmail interfaces, implementing strict content security policies, and deploying web application firewalls that can detect and block malicious JavaScript payloads. Network-level protections including email filtering solutions that scan attachments for malicious code and browser-based security controls that restrict JavaScript execution in email contexts provide additional defense layers. Regular security assessments and user awareness training should emphasize the dangers of opening untrusted email attachments, particularly those containing executable content. The vulnerability highlights the importance of implementing defense-in-depth strategies that protect against multiple attack vectors simultaneously, as demonstrated by the ATT&CK framework's emphasis on multiple defensive techniques to counter sophisticated attacks.