CVE-2006-0046 in adzapper
Summary
by MITRE
squid_redirect script in adzapper before 2006-01-29 allows remote attackers to cause a denial of service (CPU consumption) via a URL with a large number of trailing / (forward slashes), which might produce inefficient regular expressions.
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Analysis
by VulDB Data Team • 07/22/2019
The vulnerability identified as CVE-2006-0046 affects the squid_redirect script component within the adzapper software suite prior to the January 29, 2006 release. This issue represents a classic denial of service vulnerability that exploits inefficient regular expression processing within the URL parsing mechanism. The flaw manifests when the squid_redirect script encounters URLs containing an excessive number of trailing forward slashes, creating a scenario where the regular expression engine becomes overwhelmed with computational overhead.
The technical implementation of this vulnerability stems from the script's inadequate handling of URL normalization and regular expression compilation. When processing URLs with numerous trailing slashes, the adzapper software fails to implement proper input sanitization or rate limiting mechanisms. This deficiency allows attackers to craft malicious URLs that, when processed by the squid_redirect script, generate exponentially complex regular expressions that consume disproportionate CPU resources. The vulnerability operates at the application layer and specifically targets the URL rewriting and redirection functionality that squid typically handles.
From an operational perspective, this vulnerability presents a significant risk to network infrastructure as it allows remote attackers to perform resource exhaustion attacks against systems running vulnerable versions of adzapper. The impact extends beyond simple service disruption to potentially affecting the broader network performance, as the CPU consumption can escalate rapidly with minimal input from the attacker. This makes the vulnerability particularly dangerous in environments where squid serves as a critical caching or proxy service, as it could lead to cascading failures affecting multiple network services.
The vulnerability aligns with CWE-1321, which addresses the improper handling of regular expressions in applications, and demonstrates characteristics consistent with attack patterns documented in the ATT&CK framework under T1499.1 for network denial of service. Organizations implementing adzapper or similar proxy redirection software should prioritize immediate patching to address this vulnerability. Mitigation strategies include implementing URL length limits, regular expression timeout mechanisms, and input validation that prevents the processing of URLs with excessive trailing slashes. Additionally, network monitoring should be enhanced to detect unusual CPU consumption patterns that might indicate exploitation attempts. The vulnerability underscores the importance of proper input validation and regular expression optimization in network security applications, particularly those handling user-supplied data through proxy or redirection services.