CVE-2025-30349 in IMP
Summary
by MITRE • 03/21/2025
Horde IMP through 6.2.27, as used with Horde Application Framework through 5.2.23, allows XSS that leads to account takeover via a crafted text/html e-mail message with an onerror attribute (that may use base64-encoded JavaScript code), as exploited in the wild in March 2025.
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Analysis
by VulDB Data Team • 06/07/2025
This vulnerability represents a critical cross-site scripting flaw in the Horde IMP email client component that affects versions through 6.2.27 when used with Horde Application Framework through 5.2.23. The security issue stems from insufficient input validation and output sanitization of email content, particularly when processing text/html email messages. Attackers can exploit this weakness by crafting malicious email messages containing HTML elements with onerror attributes that execute arbitrary JavaScript code when rendered in the email client interface. The exploitation technique leverages base64-encoded JavaScript payloads within the onerror attribute, allowing attackers to bypass standard security filters and execute malicious scripts in the context of the victim's browser session. This vulnerability falls under CWE-79 which specifically addresses cross-site scripting flaws in web applications, and aligns with ATT&CK technique T1566.001 for initial access through spearphishing with attachments.
The operational impact of this vulnerability is severe as it enables attackers to perform account takeover operations by executing malicious JavaScript code within the victim's browser session. When a user opens the crafted email message, the embedded onerror attribute triggers JavaScript execution that can steal session cookies, credentials, or perform other malicious actions on behalf of the authenticated user. The vulnerability's exploitation in the wild during March 2025 demonstrates its real-world threat level and the active use of this technique by threat actors targeting email systems. The attack vector specifically targets the email rendering engine of the Horde IMP client, making it particularly dangerous for organizations that rely on this email infrastructure for business communications.
The technical implementation of this exploit relies on the HTML onerror attribute which is commonly used for error handling in image elements and other HTML components. When an image fails to load, the onerror handler executes JavaScript code, and attackers can craft email messages that contain specially formatted HTML that triggers these error handlers when the email client renders the content. The base64 encoding component adds an additional layer of obfuscation that helps evade signature-based detection systems and makes the malicious payload less obvious to casual inspection. This technique exploits the trust relationship between the email client and the user's browser session, allowing attackers to execute code with the privileges of the logged-in user.
Organizations should implement immediate mitigations including upgrading to patched versions of Horde IMP and Horde Application Framework, as well as implementing email content filtering that blocks or sanitizes HTML content with onerror attributes. Network-level protections such as web application firewalls can help detect and block malicious payloads, while user education about suspicious email attachments and content remains crucial. Security teams should also consider implementing strict email sanitization policies that remove or neutralize potentially dangerous HTML attributes from incoming email messages. The vulnerability demonstrates the importance of proper input validation and output encoding in web applications, particularly when handling untrusted content from external sources, and reinforces the need for comprehensive security testing of email rendering components.