CVE-2018-7212 in Sinatra
Summary
by MITRE
An issue was discovered in rack-protection/lib/rack/protection/path_traversal.rb in Sinatra 2.x before 2.0.1 on Windows. Path traversal is possible via backslash characters.
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Analysis
by VulDB Data Team • 02/08/2023
The vulnerability identified as CVE-2018-7212 represents a critical path traversal flaw in the Sinatra web framework version 2.x prior to 2.0.1, specifically affecting Windows operating systems. This issue resides within the rack-protection library at rack-protection/lib/rack/protection/path_traversal.rb, where the framework fails to properly sanitize backslash characters in file path requests. The vulnerability stems from inadequate input validation and sanitization mechanisms that allow malicious actors to exploit the path traversal mechanism through backslash encoding, which is particularly problematic on Windows systems where backslashes serve as directory separators.
The technical implementation of this vulnerability exploits the fundamental difference in how Windows and Unix-like systems handle directory separators, creating a window of opportunity for attackers to manipulate file paths through backslash characters. When Sinatra processes incoming requests containing backslash-encoded paths, the application fails to normalize or properly validate these inputs against a whitelist of acceptable characters, allowing attackers to traverse the file system hierarchy beyond intended boundaries. This flaw specifically affects Windows environments because the backslash character is interpreted differently than forward slashes, enabling attackers to bypass normal path validation checks that would otherwise prevent directory traversal attacks.
The operational impact of this vulnerability extends beyond simple file access, as successful exploitation could enable attackers to read arbitrary files on the server, potentially exposing sensitive configuration data, user credentials, or application source code. Attackers could leverage this vulnerability to access system files, application logs, or even database connection strings stored in configuration files. The vulnerability is particularly dangerous in web applications that serve dynamic content or have file upload capabilities, as it could allow for complete system compromise through the retrieval of critical system files or the execution of arbitrary code. This represents a high-severity issue that aligns with CWE-22 Path Traversal vulnerabilities, which are categorized under the broader category of injection flaws in the CWE hierarchy.
Organizations running affected versions of Sinatra on Windows systems face significant risk of data breaches and system compromise. The vulnerability requires minimal exploitation effort and can be automated through common web application attack tools. Mitigation strategies must include immediate patching to version 2.0.1 or later, which addresses the path traversal issue by implementing proper backslash sanitization and normalization. Additionally, implementing web application firewalls with path traversal detection capabilities, enforcing strict input validation at the application level, and conducting regular security assessments of web applications can help reduce the risk of exploitation. The ATT&CK framework categorizes this type of vulnerability under T1083 File and Directory Discovery, highlighting the reconnaissance phase that attackers use to map the target system's file structure. Organizations should also consider implementing principle of least privilege access controls and regular security monitoring to detect potential exploitation attempts.