CVE-2007-2164 in Konqueror
Summary
by MITRE
Konqueror 3.5.5 release 45.4 allows remote attackers to cause a denial of service (browser crash or abort) via JavaScript that matches a regular expression against a long string, as demonstrated using /(.)*/.
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Analysis
by VulDB Data Team • 08/29/2018
The vulnerability identified as CVE-2007-2164 affects Konqueror web browser version 3.5.5 release 45.4 and represents a classic example of a regular expression denial of service attack. This flaw demonstrates how seemingly benign JavaScript functionality can be exploited to disrupt browser operations through carefully crafted input patterns. The vulnerability specifically targets the browser's JavaScript engine's handling of regular expression matching operations when processing long strings, creating a condition where the engine becomes overwhelmed and ultimately crashes or aborts the browser process. This type of vulnerability falls under the broader category of resource exhaustion attacks that exploit inefficient algorithmic implementations in software components.
The technical implementation of this vulnerability exploits a specific pattern in regular expression processing where the regex pattern `/(.)*/` is used against exceptionally long strings. This particular pattern creates a catastrophic backtracking scenario in the regular expression engine, where the matching algorithm must evaluate an exponentially growing number of possible matches as the input string length increases. The vulnerability is particularly insidious because it requires minimal user interaction beyond visiting a malicious webpage containing the crafted JavaScript code. The attack vector operates entirely through client-side JavaScript execution, making it difficult to detect through traditional network-based security measures. This behavior aligns with CWE-400, which classifies the vulnerability as a resource exhaustion issue, and demonstrates the underlying weakness in the regular expression engine's backtracking algorithm implementation.
The operational impact of CVE-2007-2164 extends beyond simple browser disruption to represent a broader threat to user productivity and system availability. When exploited successfully, the vulnerability causes complete browser termination, forcing users to manually restart their browsing sessions and potentially lose unsaved work or session data. The attack can be particularly effective in environments where users frequently access untrusted websites or where automated browser testing is performed. From an attacker perspective, this vulnerability provides a reliable method for causing service disruption without requiring sophisticated exploitation techniques or elevated privileges. The vulnerability also demonstrates the importance of proper input validation and resource management in interpreted scripting languages, as the regular expression engine fails to implement adequate safeguards against pathological input patterns. This weakness can be categorized under ATT&CK technique T1499.004, which covers network denial of service attacks, and specifically represents a client-side service disruption vector.
Mitigation strategies for CVE-2007-2164 focus on both immediate remediation and long-term architectural improvements. The most direct solution involves updating to a newer version of Konqueror where the regular expression engine has been patched to prevent catastrophic backtracking scenarios. Security administrators should also implement content filtering measures that can detect and block known malicious JavaScript patterns before they reach the browser. Browser security policies should include restrictions on JavaScript execution capabilities, particularly for untrusted content sources. Additionally, implementing proper input validation and resource limits for regular expression operations can prevent similar vulnerabilities from manifesting in other software components. Organizations should consider deploying web application firewalls or security proxies that can monitor and filter malicious JavaScript patterns, as this vulnerability represents a classic example of how client-side scripting can be weaponized for denial of service attacks. The broader lesson from this vulnerability emphasizes the critical need for algorithmic complexity analysis in security-critical software components and the importance of implementing proper bounds checking and resource management in interpreted languages.