CVE-2006-2769 in Snort
Summary
by MITRE
The HTTP Inspect preprocessor (http_inspect) in Snort 2.4.0 through 2.4.4 allows remote attackers to bypass "uricontent" rules via a carriage return (\r) after the URL and before the HTTP declaration.
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Analysis
by VulDB Data Team • 06/21/2025
The vulnerability described in CVE-2006-2769 represents a significant flaw in the Snort network intrusion detection system's HTTP inspection capabilities. This issue affects versions 2.4.0 through 2.4.4 of the Snort software, which was widely deployed for network security monitoring and threat detection. The vulnerability specifically targets the http_inspect preprocessor module, which is responsible for analyzing HTTP traffic and applying various detection rules including the uricontent rule type that examines URL content for malicious patterns.
The technical flaw exploits a weakness in how the http_inspect module processes HTTP request parsing, particularly when handling carriage return characters within URL sequences. When a remote attacker crafts a malicious HTTP request containing a carriage return character immediately following the URL portion and preceding the HTTP method declaration, the preprocessor fails to properly normalize or validate this sequence. This improper handling allows the attacker to bypass uricontent rules that are designed to detect specific patterns within URLs, effectively evading detection mechanisms that rely on these rules for identifying malicious web traffic.
The operational impact of this vulnerability is substantial as it enables attackers to circumvent critical security controls implemented through Snort's signature-based detection system. Organizations relying on Snort for web application firewall functionality or HTTP traffic monitoring would experience reduced security effectiveness, as malicious payloads could be transmitted undetected through the network. The vulnerability particularly affects web application security monitoring where URL content inspection is crucial for identifying SQL injection attempts, cross-site scripting attacks, or other web-based threats that are typically detected through uricontent rules.
This vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and demonstrates how improper handling of special characters in protocol parsing can lead to security bypasses. From an ATT&CK perspective, this vulnerability relates to T1071.004 for Application Layer Protocol: DNS and T1566.001 for Phishing: Spearphishing Attachment, as it enables attackers to bypass network security controls that would otherwise detect malicious web traffic. The flaw essentially creates a path for attackers to perform evasion techniques against network-based security systems, making it particularly dangerous in environments where Snort serves as a primary detection mechanism.
The recommended mitigation strategy involves upgrading to Snort version 2.4.5 or later, where this vulnerability has been addressed through improved HTTP parsing and normalization of special characters within URL sequences. Additionally, network administrators should consider implementing complementary security controls such as web application firewalls, intrusion prevention systems, and regular security audits to reduce dependency on any single detection mechanism. Organizations should also review their existing uricontent rules to ensure they account for potential variations in HTTP request formatting and implement additional validation layers to detect anomalous HTTP traffic patterns that might indicate exploitation attempts.