CVE-2007-3929 in Web Browser
Summary
by MITRE
Use-after-free vulnerability in the BitTorrent support in Opera before 9.22 allows user-assisted remote attackers to execute arbitrary code via a crafted header in a torrent file, which leaves a dangling pointer to an invalid object.
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Analysis
by VulDB Data Team • 06/07/2025
The vulnerability described in CVE-2007-3929 represents a critical use-after-free flaw within Opera's BitTorrent implementation that existed prior to version 9.22. This type of vulnerability occurs when a program continues to reference memory that has already been freed, creating a dangling pointer condition that can be exploited by malicious actors. The specific context of this vulnerability involves Opera's handling of torrent files, which are commonly used for peer-to-peer file sharing and contain metadata about files being shared across the network. When Opera processes these torrent files, it parses various headers and metadata structures that define the file distribution parameters and peer connections.
The technical flaw manifests in how Opera's BitTorrent support manages memory allocation and deallocation when processing torrent file headers. When a crafted torrent file is encountered, the application's parser fails to properly validate or handle certain header fields, leading to a situation where memory previously allocated for torrent metadata structures is freed but the program continues to reference that memory location. This creates a use-after-free condition that can be leveraged by attackers to manipulate the program's memory state and potentially execute arbitrary code with the privileges of the user running Opera. The vulnerability specifically requires user-assisted remote exploitation, meaning a user must intentionally open or process the malicious torrent file, typically through a web download or file sharing mechanism.
The operational impact of this vulnerability extends beyond simple code execution, as it represents a significant security risk for users who engage with peer-to-peer file sharing or download content from untrusted sources. Attackers can craft malicious torrent files that, when processed by vulnerable Opera versions, could lead to complete system compromise. The use-after-free condition allows for memory corruption that can be exploited through various techniques including return-oriented programming or direct code injection, depending on the target system's memory layout and security mitigations. This vulnerability particularly affects users who rely on Opera's built-in BitTorrent support for downloading files, making it a significant concern for the browser's user base.
Mitigation strategies for CVE-2007-3929 primarily involve updating to Opera version 9.22 or later, which contains the necessary patches to address the memory management issues in the BitTorrent implementation. Organizations and users should also implement additional security measures such as disabling BitTorrent support in web browsers when not required, using network monitoring tools to detect suspicious torrent file activity, and maintaining up-to-date security patches for all software components. The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions in software implementations. From an ATT&CK framework perspective, this vulnerability maps to techniques involving code injection and privilege escalation, as the exploitation can lead to arbitrary code execution with elevated privileges. Security professionals should also consider implementing browser isolation techniques and network segmentation to limit the potential impact of such vulnerabilities in enterprise environments.