CVE-2015-9279 in MailEnable
Summary
by MITRE
MailEnable before 8.60 allows Stored XSS via malformed use of "<img/src" with no ">" character in the body of an e-mail message.
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Analysis
by VulDB Data Team • 05/02/2020
The vulnerability identified as CVE-2015-9279 affects MailEnable versions prior to 8.60 and represents a stored cross-site scripting flaw that can be exploited through carefully crafted email messages. This vulnerability specifically targets the email client's handling of malformed html content within message bodies, creating a persistent security risk that can affect users who process these malicious emails. The flaw stems from insufficient input validation and sanitization of email content, particularly when processing html elements that contain malformed image tags. The vulnerability is classified as a stored XSS attack because the malicious payload is embedded within the email message itself and remains persistent until the message is processed by the vulnerable system.
The technical implementation of this vulnerability involves the exploitation of how MailEnable parses html content when rendering email messages. Attackers can craft email messages containing malformed "<img/src" tags that lack the closing ">" character, which causes the email client to improperly handle the html structure during rendering. This parsing error creates an opportunity for malicious javascript code to be executed within the context of the victim's browser session when they view the compromised email. The absence of proper html sanitization allows attackers to inject malicious payloads that can execute arbitrary code, potentially leading to session hijacking, data theft, or further exploitation of the victim's system. This type of vulnerability falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly sanitize user input that gets rendered in web contexts.
The operational impact of CVE-2015-9279 extends beyond simple email compromise, as it can enable attackers to gain unauthorized access to user accounts and potentially escalate privileges within the email system. When users open malicious emails containing this crafted payload, the stored XSS vulnerability can trigger malicious scripts that steal authentication tokens, redirect users to phishing sites, or execute additional attacks against the victim's system. The persistence of this vulnerability means that once an email with the malicious content is delivered to a user's inbox, the attack vector remains active until the email is deleted or the system is patched. This makes the vulnerability particularly dangerous in enterprise environments where email is a primary communication channel and users may not immediately recognize the malicious nature of the content.
Organizations affected by this vulnerability should prioritize immediate remediation through patching MailEnable to version 8.60 or later, which contains the necessary fixes for the html sanitization issues. Additionally, network administrators should implement email filtering rules that can detect and block malformed html content, particularly focusing on image tags without proper closing characters. The implementation of Content Security Policy headers and browser-based security measures can provide additional defense in depth against exploitation attempts. Security teams should also conduct thorough vulnerability assessments to ensure no other systems in the environment are susceptible to similar stored XSS vulnerabilities, particularly those that process user-supplied content through web interfaces. This vulnerability demonstrates the critical importance of proper input validation and output encoding in web applications, aligning with ATT&CK technique T1566.001 - Phishing: Spearphishing Attachment, where the initial compromise often occurs through malicious email attachments or embedded content that executes in the user's browser context.