CVE-2025-70515 in Fanvil
Summary
by MITRE • 10/07/2026
The device log component of Fanvil x7a firmware version 2.6.0.1182 does not properly sanitize or encode reflected user supplied data. The lack of sanitization allows for the injection of HTML which can be used to execute malicious JavaScript code on any target browser which renders the device log component.
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified in Fanvil x7a firmware version 2.6.0.1182 represents a classic instance of Cross-Site Scripting, specifically categorized under CWE-79: Improper Neutralization of Input During Web Page Generation. This flaw resides within the device log component, which is responsible for displaying operational logs to administrators or users via a web interface. The core technical deficiency lies in the application's failure to properly sanitize or encode user-supplied data before rendering it back into the HTML document structure. When an attacker inputs malicious content that includes HTML tags and JavaScript code snippets, the server processes this input without applying necessary escaping mechanisms such as converting special characters like less-than signs, greater-than signs, ampersands, and quotes into their corresponding HTML entities. Consequently, when the log page is loaded in a victim's browser, the browser interprets these injected strings not as plain text but as executable code within the context of the application's domain.
From an operational perspective, this vulnerability allows for significant security implications beyond simple script execution. Because the malicious JavaScript runs with the same privileges and permissions as the legitimate web application, it can access session cookies, local storage data, and other sensitive information stored by the browser. An attacker could leverage this capability to hijack administrative sessions, effectively impersonating a valid user without needing their credentials. Furthermore, the injected script can perform actions on behalf of the victim, such as modifying configuration settings, triggering unauthorized calls, or exfiltrating confidential log data containing network topology details and internal IP addresses. This scenario aligns with several techniques in the MITRE ATT&CK framework, particularly T1059: Command and Scripting Interpreter for executing code within a browser environment, and potentially T1078: Valid Accounts if session hijacking is successful to gain persistent access or escalate privileges within the VoIP infrastructure.
The impact extends beyond individual user compromise as it can facilitate broader attacks against the network hosting the Fanvil device. By using the compromised web interface as a pivot point, an attacker might attempt further lateral movement or exploit other vulnerabilities in connected systems that trust sessions originating from this domain. Additionally, if the log component is accessible to multiple users on different machines within the same local area network, a single injection could lead to widespread compromise through stored XSS mechanisms where the malicious payload remains active until manually cleared by an administrator. This persistence makes remediation more complex and increases the window of exposure for sensitive organizational data.
Mitigation strategies must address both immediate technical fixes and broader security hygiene practices. The primary remedy involves implementing strict input validation and output encoding on the server side before any user-supplied data is rendered into HTML responses. Developers should employ context-aware encoding techniques that ensure special characters are safely escaped regardless of where they appear in the document structure, whether inside an attribute value, a script block, or plain text. Additionally, deploying Content Security Policy headers can significantly reduce the impact by restricting which sources scripts are allowed to load from and preventing inline script execution unless explicitly whitelisted. Regular firmware updates provided by Fanvil should be applied promptly as they typically contain patches for such input sanitization issues. Finally, implementing robust session management practices, including short-lived tokens and secure cookie flags like HttpOnly and Secure, can mitigate the risk of session hijacking even if a successful XSS attack occurs.