CVE-2013-1055 in unity-firefox-extension
Summary
by MITRE • 04/08/2021
The unity-firefox-extension package could be tricked into dropping a C callback which was still in use, which Firefox would then free, causing Firefox to crash. This could be achieved by adding an action to the launcher and updating it with new callbacks until the libunity-webapps rate limit was hit. Fixed in 3.0.0+14.04.20140416-0ubuntu1.14.04.1 of unity-firefox-extension and in all versions of libunity-webapps by shipping an empty unity-firefox-extension package, thus disabling the extension entirely and invalidating the attack against the libunity-webapps package.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 04/11/2021
The vulnerability identified as CVE-2013-1055 affects the unity-firefox-extension package within Ubuntu's desktop environment ecosystem, specifically targeting the interaction between Firefox and the libunity-webapps library. This issue represents a classic use-after-free vulnerability where memory management fails to properly track object references, creating a scenario where Firefox attempts to free memory that is still actively referenced by the Unity extension. The flaw manifests when the extension incorrectly handles callback registration and deregistration processes, leading to a situation where a callback function remains in use while the system believes it has been safely deallocated.
The technical exploitation of this vulnerability occurs through a carefully orchestrated sequence of actions that leverages the rate limiting mechanism within libunity-webapps. Attackers can systematically add actions to the Firefox launcher and continuously update these actions with new callback functions until the system reaches its configured rate limit. This process effectively exhausts the extension's callback management capacity, creating a memory state where previously used callbacks are freed while still being referenced by active Firefox processes. The vulnerability is particularly concerning as it demonstrates how seemingly benign extension functionality can be weaponized to cause denial-of-service conditions that crash the entire browser application.
The operational impact of this vulnerability extends beyond simple browser crashes, as it represents a potential vector for more sophisticated attacks within the Ubuntu desktop environment. When Firefox crashes due to this memory management error, it can disrupt user productivity and potentially provide attackers with opportunities to escalate privileges or execute additional malicious code. The vulnerability affects specific versions of the unity-firefox-extension package and libunity-webapps library, with the fix implemented through a complete disablement of the extension rather than a targeted code patch. This approach, while effective, represents a defensive measure that removes the extension entirely from the system rather than addressing the underlying memory management issue.
The remediation strategy for CVE-2013-1055 involved shipping an empty unity-firefox-extension package that effectively disables the entire extension functionality, thereby preventing any further exploitation attempts. This solution, while pragmatic, aligns with the principle of least privilege and defense in depth by eliminating the attack surface entirely. The fix addresses the core issue by preventing the problematic callback handling behavior that led to the use-after-free condition, though it does so at the cost of removing useful desktop integration functionality. This vulnerability demonstrates the importance of proper memory management in desktop extension systems and highlights how seemingly isolated components can create cascading failures that impact core applications. The issue falls under CWE-415 which describes double free conditions and CWE-416 which covers use after free vulnerabilities, both of which are fundamental memory safety concerns that require careful attention in desktop application environments.
The attack vector for this vulnerability specifically targets the interaction between Firefox and Ubuntu's Unity desktop environment, making it particularly relevant for users of Ubuntu 14.04 and similar distributions. The exploitation requires specific conditions to be met, including the presence of the vulnerable unity-firefox-extension package and the ability to interact with the Firefox launcher interface. The rate limiting mechanism that enables this attack provides insight into how modern desktop environments must carefully balance functionality with security, as features that provide convenience can inadvertently create security weaknesses. Organizations and users should consider the broader implications of desktop extension ecosystems, particularly when these components interact with core applications like web browsers. The vulnerability also demonstrates how the ATT&CK framework's concept of privilege escalation through application vulnerabilities can manifest in desktop environments where extensions have elevated access to system resources.