CVE-2005-1994 in SurfinGate
Summary
by MITRE
Finjan SurfinGate 7.0SP2 and SP3 allows remote attackers to download blocked files via hex-encoded characters in a filename, as demonstrated using "%2e".
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Analysis
by VulDB Data Team • 06/07/2019
The vulnerability identified as CVE-2005-1994 affects Finjan SurfinGate 7.0 Service Pack 2 and 3 web security appliances, representing a significant bypass flaw in content filtering mechanisms. This vulnerability exploits a weakness in the filename validation process where the system fails to properly decode and validate hex-encoded characters within file names, allowing malicious actors to circumvent content blocking policies. The specific demonstration uses the "%2e" hex encoding which represents a period character, enabling attackers to manipulate the filtering system's behavior.
The technical flaw resides in the insufficient input sanitization and validation logic within the SurfinGate appliance's file handling routines. When processing filenames containing hex-encoded characters, the system does not properly decode these sequences before applying content filtering rules, creating a path traversal and content bypass opportunity. This represents a classic input validation vulnerability where the system assumes that all input is properly formatted and does not account for encoded representations that could be used to evade detection mechanisms. The vulnerability aligns with CWE-20, which describes improper input validation, and specifically relates to CWE-77, which addresses command injection through improper input handling.
The operational impact of this vulnerability is substantial as it allows remote attackers to download files that should be blocked by the security appliance's content filtering policies. Attackers can leverage this weakness to bypass restrictions on malicious file types such as executables, scripts, or other potentially harmful content. The hex encoding technique demonstrates a sophisticated approach to evasion that could be extended to other encoded characters, potentially allowing access to a wide range of blocked content. This vulnerability essentially undermines the core security function of the appliance by enabling unauthorized content access through manipulation of encoded filenames.
Organizations utilizing Finjan SurfinGate appliances are at risk of data exfiltration, malware deployment, and unauthorized access to restricted content. The vulnerability could be exploited in conjunction with other attack vectors to create more complex compromise scenarios, potentially allowing attackers to establish persistent access or escalate privileges within the network. Security administrators should consider this vulnerability as part of a broader threat landscape where attackers seek to bypass network security controls through various encoding and obfuscation techniques. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under the T1071.004 sub-technique for application layer protocol: web protocols, where attackers manipulate web traffic to evade detection mechanisms.
Mitigation strategies should include applying the vendor-provided security patches for SurfinGate 7.0 Service Pack 2 and 3, implementing additional network monitoring to detect anomalous filename patterns, and enhancing logging mechanisms to capture and analyze hex-encoded character usage in file transfers. Organizations should also consider implementing network segmentation and additional content filtering layers to reduce the impact of such bypasses. The vulnerability highlights the importance of proper input validation and the need for comprehensive testing of security appliances against various encoding techniques. Regular security assessments and vulnerability scanning should include testing for similar encoding bypass techniques to ensure that security controls remain effective against evolving attack methodologies.