CVE-2015-7242 in FRITZ!OS
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Push-Service-Mails feature in AVM FRITZ!OS before 6.30 allows remote attackers to inject arbitrary web script or HTML via the display name in the FROM field of an SIP INVITE message.
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Analysis
by VulDB Data Team • 07/02/2022
The CVE-2015-7242 vulnerability represents a critical cross-site scripting flaw within the Push-Service-Mails functionality of AVM FRITZ!OS versions prior to 6.30. This vulnerability specifically targets the handling of SIP INVITE messages, which are fundamental components of the Session Initiation Protocol used for establishing multimedia communication sessions including voice and video calls. The vulnerability arises from insufficient input validation and sanitization of the display name field within the FROM header of SIP messages, creating an avenue for malicious actors to execute arbitrary web scripts or HTML code within the context of a victim's browser.
The technical exploitation of this vulnerability occurs through the manipulation of the display name parameter in SIP INVITE messages, which are commonly used in VoIP communications. When a victim's FRITZ!Box device processes these maliciously crafted SIP messages, the system fails to properly sanitize the display name field before rendering it in the user interface. This allows attackers to inject malicious HTML content or JavaScript code that executes when users view the incoming call information or message notifications. The vulnerability specifically affects the Push-Service-Mails feature, which is designed to notify users of incoming communications through push notifications, making it particularly dangerous as users may unknowingly interact with these malicious payloads.
From an operational impact perspective, this vulnerability creates significant security risks for users of AVM FRITZ!Box devices, as it enables remote code execution through social engineering attacks. Attackers can craft malicious SIP messages that appear to originate from legitimate sources, tricking users into executing malicious code when they view notifications. The vulnerability affects the broader VoIP ecosystem, as it exploits a fundamental weakness in how SIP messages are processed and displayed. This type of vulnerability aligns with CWE-79, which describes Cross-site Scripting flaws, and represents a classic example of how insecure input handling can lead to privilege escalation and unauthorized code execution. The attack vector is particularly concerning because it requires minimal user interaction beyond receiving a legitimate-looking communication, making it an effective tool for phishing and malware distribution.
The mitigation strategy for this vulnerability involves updating AVM FRITZ!OS devices to version 6.30 or later, which includes proper input sanitization and validation for SIP message fields. Network administrators should implement SIP message filtering and validation at the network perimeter to prevent malicious SIP messages from reaching end-user devices. Additionally, organizations should consider implementing network segmentation to isolate VoIP traffic and reduce the potential impact of such attacks. The vulnerability demonstrates the importance of secure coding practices in telecommunications protocols and highlights the need for comprehensive input validation across all message handling components. This issue also relates to ATT&CK technique T1566, which covers phishing and social engineering attacks, as the vulnerability can be exploited through deceptive communication methods that appear legitimate to users. Organizations should conduct regular security assessments of their VoIP infrastructure and maintain up-to-date firmware to protect against similar vulnerabilities in the future.