CVE-2007-1563 in Web Browser
Summary
by MITRE
The FTP protocol implementation in Opera 9.10 allows remote attackers to allows remote servers to force the client to connect to other servers, perform a proxied port scan, or obtain sensitive information by specifying an alternate server address in an FTP PASV response.
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Analysis
by VulDB Data Team • 01/14/2025
The vulnerability described in CVE-2007-1563 represents a significant security flaw in Opera 9.10's implementation of the File Transfer Protocol that enables malicious FTP servers to manipulate client behavior in ways that compromise user security. This issue specifically affects the Passive FTP mode implementation where the client expects the server to provide an IP address and port number for data connection establishment. The flaw allows remote attackers to inject alternate server addresses within the PASV response, creating a vector for various malicious activities that can bypass normal network security controls.
The technical mechanism behind this vulnerability stems from insufficient validation of server responses in Opera's FTP client implementation. When an FTP server responds to a PASV command, it typically provides an IP address and port number that the client uses to establish a data connection. In this case, Opera 9.10 fails to properly validate the IP address provided in the PASV response, allowing attackers to specify arbitrary IP addresses that may point to internal network resources or other systems. This validation failure creates a path for attackers to manipulate the client's network behavior and potentially gain unauthorized access to network resources that would normally be protected by firewalls or network segmentation.
The operational impact of this vulnerability extends beyond simple information disclosure and includes the potential for active network reconnaissance and exploitation. Attackers can leverage this flaw to perform proxied port scans by having the vulnerable Opera client attempt connections to various ports on target systems, effectively using the client as a proxy for network scanning activities. This capability undermines the fundamental security assumptions of network isolation and firewall protection, as the client's connection attempts can traverse network boundaries through the trusted FTP server. Additionally, the vulnerability enables sensitive information gathering by allowing attackers to force the client to connect to systems that might reveal internal network topology, service configurations, or other sensitive data through the connection process.
This vulnerability aligns with several cybersecurity frameworks and threat modeling concepts, particularly those related to protocol implementation flaws and man-in-the-middle attack vectors. From a CWE perspective, this issue maps to CWE-20: Improper Input Validation, as the application fails to properly validate input from untrusted sources. The vulnerability also relates to CWE-1236: Use of Untrusted Input in a Security Decision, since the client makes security-sensitive decisions based on unvalidated server responses. The ATT&CK framework categorizes this under T1046: Network Service Scanning and T1190: Exploit Public-Facing Application, as it represents an attack vector that exploits a client-side application to perform reconnaissance and potentially gain further access to network resources.
Mitigation strategies for this vulnerability require both immediate and long-term approaches to address the root cause and prevent exploitation. The most effective immediate solution involves updating to a patched version of Opera that properly validates FTP server responses and implements stricter input validation for PASV responses. Network administrators should also implement additional security controls such as FTP filtering at network boundaries and monitoring for suspicious FTP activity patterns that might indicate exploitation attempts. Organizations should consider implementing application whitelisting policies that restrict which FTP clients can be used in environments where such vulnerabilities might be exploited. Additionally, security awareness training for users about the risks of connecting to untrusted FTP servers can help reduce the attack surface. The vulnerability also highlights the importance of proper protocol implementation validation and the need for security testing of client applications that handle network communications, particularly those that operate in potentially hostile network environments where they might be subject to manipulation by remote attackers.