CVE-2015-4657 in Mailbird
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Mailbird 2.0.16.0 and earlier allows remote attackers to inject arbitrary web script or HTML via an e-mail message body with a crafted URL.
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Analysis
by VulDB Data Team • 04/10/2019
The vulnerability identified as CVE-2015-4657 represents a critical cross-site scripting flaw within Mailbird email client version 2.0.16.0 and earlier releases. This security weakness resides in the application's handling of email message bodies, specifically when processing crafted URLs that contain malicious script content. The vulnerability enables remote attackers to execute arbitrary web scripts or HTML code within the context of a victim's browser session, exploiting the client's insufficient input validation mechanisms.
The technical implementation of this XSS vulnerability stems from Mailbird's failure to properly sanitize and escape user-controllable input received through email message bodies. When a user views an email containing a maliciously crafted URL, the application processes the URL without adequate filtering or encoding, allowing malicious scripts to execute in the browser context. This flaw operates under CWE-79 which categorizes cross-site scripting vulnerabilities as weaknesses in web applications that allow attackers to inject client-side scripts into web pages viewed by other users. The vulnerability specifically manifests when the email client renders URLs that contain embedded JavaScript or HTML content within the message display area.
The operational impact of this vulnerability extends beyond simple script execution, potentially enabling sophisticated attack vectors including session hijacking, credential theft, and data exfiltration. An attacker could craft malicious emails that, when opened by a victim, would execute scripts designed to capture browser cookies, redirect users to phishing sites, or even download and execute additional malware. The remote nature of this attack means that exploitation does not require physical access to the target system, making it particularly dangerous in enterprise environments where email is a primary communication channel. This vulnerability aligns with ATT&CK technique T1566 which covers social engineering tactics involving phishing and spearphishing attacks that leverage client-side vulnerabilities.
Mitigation strategies for this vulnerability should focus on immediate remediation through software updates to versions that properly implement input validation and output encoding. Organizations should implement email filtering solutions that can detect and block suspicious URL patterns within email content. The application should enforce strict content sanitization policies that escape or remove potentially dangerous characters from email message bodies before rendering them in the user interface. Security awareness training for end users remains crucial to prevent accidental interaction with malicious emails, while network-level protections such as web application firewalls can provide additional defense-in-depth measures against exploitation attempts.