CVE-2006-0294 in Firefox
Summary
by MITRE
Mozilla Firefox before 1.5.0.1, Thunderbird 1.5 if running Javascript in mail, and SeaMonkey before 1.0 allow remote attackers to execute arbitrary code by changing an element s style from position:relative to position:static, which causes Gecko to operate on freed memory.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 07/07/2021
This vulnerability represents a critical heap-based buffer overflow in the Gecko rendering engine that affects multiple Mozilla products including Firefox versions prior to 1.5.0.1, Thunderbird 1.5 with JavaScript enabled, and SeaMonkey versions before 1.0. The flaw occurs during the processing of CSS style changes, specifically when an element transitions from position:relative to position:static, creating a condition where the browser attempts to access memory that has already been freed. This type of vulnerability falls under CWE-416, which describes use of freed memory conditions, and represents a classic example of a memory safety issue that can lead to arbitrary code execution. The vulnerability is particularly dangerous because it can be triggered remotely through crafted web content, making it a prime target for exploitation in phishing attacks or malicious websites.
The technical exploitation mechanism involves manipulating CSS positioning properties in a way that causes the Gecko engine to improperly handle memory management during layout calculations. When an element changes from relative to static positioning, the browser's layout engine performs internal memory operations that reference previously deallocated memory blocks. This memory corruption can be leveraged by attackers to execute arbitrary code with the privileges of the user running the affected browser. The vulnerability demonstrates how seemingly benign CSS operations can trigger serious security issues when combined with improper memory management in browser engines. The exploitation requires JavaScript to be enabled in the mail client context for Thunderbird, but the core memory corruption occurs at the rendering engine level regardless of the application context.
The operational impact of this vulnerability extends beyond simple code execution to encompass complete system compromise when successful. Attackers can leverage this flaw to install malware, steal sensitive data, or perform other malicious activities without user interaction beyond visiting a compromised website. The vulnerability affects a wide range of Mozilla-based applications and persisted across multiple product lines, making it particularly concerning for organizations that rely on these browsers for email and web browsing. Security researchers have classified this vulnerability as high-risk due to its remote exploitability and the potential for privilege escalation. The vulnerability also aligns with ATT&CK technique T1059.007 for script-based execution and T1566 for social engineering through malicious websites, making it a significant threat vector in modern attack scenarios.
Mitigation strategies for this vulnerability primarily focus on immediate patching of affected software versions and implementing additional security measures. Organizations should prioritize updating to Mozilla Firefox 1.5.0.1 or later, Thunderbird 1.5 with JavaScript disabled, or SeaMonkey 1.0 and later versions to address the core memory management issue. Browser security configurations should include disabling JavaScript in mail clients where possible, as this removes one attack vector for exploitation. Network-level protections can include web application firewalls and content filtering systems that can detect and block malicious CSS content. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping their browser software updated. The vulnerability serves as a reminder of the critical importance of memory safety in browser engines and the need for regular security updates to address known heap corruption issues.