CVE-2006-3379 in Hiki Wiki
Summary
by MITRE
Algorithmic complexity vulnerability in Hiki Wiki 0.6.0 through 0.6.5 and 0.8.0 through 0.8.5 allows remote attackers to cause a denial of service (CPU consumption) by performing a diff between large, crafted pages that trigger the worst case.
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Analysis
by VulDB Data Team • 07/21/2019
The vulnerability described in CVE-2006-3379 represents a critical algorithmic complexity issue affecting Hiki Wiki versions 0.6.0 through 0.6.5 and 0.8.0 through 0.8.5. This flaw resides in the wiki's diff algorithm implementation which is responsible for comparing and displaying changes between different versions of wiki pages. The vulnerability manifests when remote attackers submit specially crafted large pages that, when processed through the diff functionality, trigger worst-case algorithmic behavior. This class of vulnerability falls under CWE-400 which specifically addresses algorithmic complexity vulnerabilities, where the computational resources required by an algorithm grow exponentially with input size rather than remaining manageable. The affected versions of Hiki Wiki utilize a diff algorithm that does not properly handle pathological input cases, leading to excessive CPU consumption during the comparison process.
The operational impact of this vulnerability is severe as it enables a remote denial of service attack that can completely consume system resources and render the wiki service unavailable to legitimate users. When an attacker submits two large, crafted pages to the diff functionality, the underlying algorithm enters into a computationally expensive worst-case scenario where the time complexity degrades from linear or polynomial to exponential behavior. This means that even relatively small increases in input size can cause dramatic increases in processing time, potentially leading to system hangs, resource exhaustion, or complete service disruption. The vulnerability specifically targets the diff algorithm's handling of page comparisons, which is a fundamental feature of wiki systems used for tracking changes and maintaining version control. Attackers can exploit this by creating pages with specific patterns that force the algorithm into its worst-case execution path, making it particularly dangerous as it can be triggered with relatively simple input manipulation.
From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks through resource exhaustion. The attack vector is remote and requires no authentication, making it particularly dangerous for publicly accessible wiki installations. The vulnerability demonstrates poor input validation and inadequate algorithmic complexity bounds checking in the software implementation. Organizations running affected versions of Hiki Wiki face significant risk as this vulnerability can be exploited by any remote user with access to the wiki's diff functionality, potentially leading to service unavailability that affects all users of the system. The exponential time complexity behavior means that even modestly sized inputs can cause substantial resource consumption, making the attack effective against systems with limited computational resources. This vulnerability type represents a classic example of how seemingly benign algorithmic operations can become catastrophic under specific input conditions, highlighting the importance of robust algorithmic analysis and proper resource management in security-critical applications.
The recommended mitigation strategy involves immediate patching of affected Hiki Wiki versions to either 0.6.6 or 0.8.6 which contain fixes for the algorithmic complexity issue. Additionally, system administrators should implement input size limits and processing time constraints on diff operations to prevent exploitation even if patching is not immediately possible. The fix typically involves implementing proper bounds checking in the diff algorithm or replacing it with a more efficient implementation that guarantees reasonable time complexity regardless of input patterns. Organizations should also consider monitoring for unusual diff processing patterns and implementing rate limiting to prevent abuse of the functionality. This vulnerability underscores the importance of algorithmic complexity analysis during software development and the necessity of testing with potentially malicious inputs to identify potential worst-case scenarios that could be exploited by attackers.