CVE-2018-14950 in SquirrelMail
Summary
by MITRE
The mail message display page in SquirrelMail through 1.4.22 has XSS via a "<svg><a xlink:href=" attack.
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Analysis
by VulDB Data Team • 04/29/2023
The vulnerability CVE-2018-14950 represents a cross-site scripting flaw in SquirrelMail version 1.4.22 and earlier, specifically affecting the mail message display functionality. This issue arises from insufficient input validation and output encoding mechanisms within the web application's rendering pipeline. The vulnerability is particularly concerning as it targets the core messaging functionality of the email client, which users interact with regularly. The attack vector involves embedding malicious svg elements with xlink:href attributes directly into email messages that are then displayed within the SquirrelMail interface, creating a persistent threat vector for attackers who can compromise user sessions or exfiltrate sensitive information.
The technical implementation of this vulnerability stems from the application's failure to properly sanitize user-supplied content before rendering it in the browser context. When a user views an email message containing the malicious svg payload with an xlink:href attribute pointing to a malicious URL, the browser executes the embedded javascript code within the context of the SquirrelMail application. This occurs because the application does not implement adequate content security policies or output encoding mechanisms to prevent the execution of untrusted code. The vulnerability is classified as a classic reflected XSS issue where the malicious payload is embedded within the email message itself, making it particularly dangerous as it can be triggered simply by viewing the compromised message.
The operational impact of this vulnerability extends beyond simple script execution, potentially enabling attackers to perform session hijacking, steal cookies, redirect users to malicious sites, or even inject additional malicious content into the user's email environment. Users who access compromised emails through the vulnerable SquirrelMail interface become potential victims of credential theft, data exfiltration, or further exploitation attempts. The vulnerability affects all users of the affected SquirrelMail versions regardless of their security awareness level, as the attack can be executed through legitimate email messages without requiring any special user interaction beyond viewing the compromised content. This makes the vulnerability particularly dangerous in enterprise environments where email is a primary communication channel.
Mitigation strategies for CVE-2018-14950 should prioritize immediate patching of the SquirrelMail application to the latest available version that contains the necessary security fixes. Organizations should also implement additional defensive measures including content security policy headers, input validation at multiple layers, and regular security assessments of web applications. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and represents a typical example of how insecure output encoding can lead to severe security implications in web-based email clients. Security teams should also consider implementing email filtering solutions that can detect and block suspicious svg content, while monitoring for anomalous user behavior that might indicate successful exploitation attempts. The ATT&CK framework categorizes this vulnerability under the T1059.007 technique for scripting languages, as the attack leverages javascript execution through malformed svg content within email messages.