CVE-2016-9470 in Adserver
Summary
by MITRE
Revive Adserver before 3.2.5 and 4.0.0 suffers from Reflected File Download. `www/delivery/asyncspc.php` was vulnerable to the fairly new Reflected File Download (RFD) web attack vector that enables attackers to gain complete control over a victim's machine by virtually downloading a file from a trusted domain.
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Analysis
by VulDB Data Team • 11/22/2022
The vulnerability identified as CVE-2016-9470 affects Revive Adserver versions prior to 3.2.5 and 4.0.0, presenting a critical security flaw that exploits the Reflected File Download (RFD) attack vector. This particular vulnerability resides within the `www/delivery/asyncspc.php` file, which serves as a delivery endpoint for ad server functionality. The RFD technique represents a sophisticated method of attack that leverages the trust relationship between web applications and their users, enabling attackers to execute malicious code through seemingly legitimate file downloads from trusted domains. The attack exploits the fundamental trust users place in their browsers when encountering file downloads, particularly when these downloads originate from domains they consider reputable.
The technical implementation of this vulnerability occurs when the asyncspc.php script fails to properly validate or sanitize user input parameters that are reflected in the response headers or content. When an attacker crafts a malicious URL containing crafted parameters, the vulnerable script reflects these parameters directly into the HTTP response, particularly within content disposition headers that dictate how browsers should handle file downloads. This reflection creates a scenario where a victim's browser receives a response that appears to originate from a legitimate ad server domain but actually prompts the download of a malicious file, often with executable extensions such as .exe, .bat, or .scr. The vulnerability specifically targets the way the application handles asynchronous ad delivery requests, making it particularly dangerous in advertising environments where users frequently interact with third-party content.
The operational impact of this vulnerability extends far beyond simple data theft or service disruption, as it enables complete compromise of victim machines through social engineering attacks. An attacker can construct malicious URLs that appear legitimate when shared through compromised advertising networks or malicious email campaigns, leading users to unknowingly download and execute malware. The attack vector is particularly effective because it leverages the trust users place in ad servers and advertising networks, making it difficult to distinguish between legitimate and malicious content. According to the CWE catalog, this vulnerability maps to CWE-502 which describes "Deserialization of Untrusted Data" and more specifically relates to CWE-434 which covers "Unrestricted Upload of File with Dangerous Type." The attack pattern aligns with the ATT&CK framework under T1195.001 "Phishing with Social Engineering" and T1059.001 "Command and Scripting Interpreter: PowerShell" as the malicious payloads often involve PowerShell scripts or other automated exploitation techniques.
Mitigation strategies for CVE-2016-9470 require immediate patching of affected Revive Adserver installations to version 3.2.5 or 4.0.0, which contain the necessary input validation and sanitization fixes. Organizations should implement comprehensive web application firewalls that can detect and block suspicious parameter patterns in ad delivery endpoints, particularly those that reflect user input in file download headers. Network administrators should monitor for unusual traffic patterns related to ad delivery endpoints and implement strict content security policies that prevent automatic execution of downloaded files. Additionally, user education programs should emphasize the importance of verifying download sources and avoiding suspicious advertising content. The vulnerability highlights the critical need for proper input validation in web applications and demonstrates how seemingly innocuous functionality can become a gateway for complete system compromise when proper security controls are absent. Organizations should conduct regular security assessments of their advertising infrastructure and implement automated scanning tools to identify similar vulnerabilities in other web applications that handle user-supplied data in file download contexts.