CVE-2019-9557 in Ability Mail Server
Summary
by MITRE
Ability Mail Server 4.2.6 has Persistent Cross Site Scripting (XSS) via the body e-mail body. To exploit the vulnerability, the victim must open an email with malicious Javascript inserted into the body of the email as an iframe.
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Analysis
by VulDB Data Team • 07/02/2024
The CVE-2019-9557 vulnerability affects Ability Mail Server version 4.2.6 and represents a persistent cross site scripting flaw that allows attackers to inject malicious javascript code into email messages. This vulnerability specifically targets the email body field where malicious scripts can be embedded and executed when victims open the compromised emails. The attack vector requires social engineering to convince users to open the malicious email, making it particularly dangerous in targeted phishing campaigns. The vulnerability stems from inadequate input validation and output encoding mechanisms within the email server's processing pipeline, allowing untrusted data to be rendered directly into the web interface without proper sanitization.
The technical implementation of this vulnerability falls under CWE-79 which describes improper neutralization of input during web page generation, specifically manifesting as cross site scripting vulnerabilities. The flaw exists because the email server fails to properly escape or filter special characters in email content before rendering it in the web interface. When an attacker crafts an email with malicious javascript code embedded in the body field, particularly using iframe tags, the server stores this content without adequate sanitization. Upon victim access to their email interface, the malicious code executes in the context of the victim's browser session, potentially compromising user credentials, accessing sensitive information, or performing unauthorized actions within the email application.
The operational impact of CVE-2019-9557 extends beyond simple script execution as it enables a wide range of malicious activities including session hijacking, data exfiltration, and privilege escalation within the email system. Attackers can leverage this vulnerability to create persistent backdoors, steal authentication tokens, or redirect users to malicious websites that appear legitimate. The persistent nature of the vulnerability means that once an attacker successfully injects malicious code, it remains active until manually removed from the email server's database. This makes the vulnerability particularly dangerous for organizations with large user bases, as a single compromised email can affect multiple users over extended periods. The attack requires minimal technical expertise from threat actors, making it attractive for both targeted attacks and automated exploitation campaigns.
Mitigation strategies for CVE-2019-9557 should focus on implementing robust input validation and output encoding mechanisms throughout the email server's processing pipeline. Organizations should immediately upgrade to a patched version of Ability Mail Server that addresses the XSS vulnerability, as no vendor patch was available at the time of reporting. Network administrators should implement email content filtering solutions that can detect and block suspicious javascript code patterns, particularly within iframe tags. The implementation of content security policies (CSP) at the web application level can provide additional protection against script execution. Regular security auditing of email server configurations and input validation mechanisms should be conducted to identify potential XSS vulnerabilities. Users should be trained to recognize suspicious email patterns and implement multi-factor authentication to reduce the impact of potential session hijacking attacks. The vulnerability also highlights the importance of following secure coding practices such as those outlined in the OWASP Secure Coding Practices, specifically focusing on input validation and output encoding to prevent cross site scripting vulnerabilities. Organizations should also consider implementing email encryption and digital signatures to add additional layers of security beyond the basic XSS protection measures.