CVE-2011-2524 in libsoup
Summary
by MITRE
Directory traversal vulnerability in soup-uri.c in SoupServer in libsoup before 2.35.4 allows remote attackers to read arbitrary files via a %2e%2e (encoded dot dot) in a URI.
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Analysis
by VulDB Data Team • 04/24/2019
The vulnerability identified as CVE-2011-2524 represents a critical directory traversal flaw within the libsoup library, specifically affecting the SoupServer component and its soup-uri.c implementation. This weakness resides in the library's handling of URI parsing and path resolution mechanisms, where the system fails to properly sanitize or validate directory traversal sequences. The vulnerability manifests when the application processes Uniform Resource Identifiers containing encoded dot-dot sequences, specifically the %2e%2e representation that translates to ../ in standard URI encoding. Attackers can exploit this by crafting malicious URIs that include these encoded sequences to navigate outside the intended directory structure and access arbitrary files on the server filesystem. The flaw exists in libsoup versions prior to 2.35.4, indicating that this was a known issue that required a specific patch to address the improper input validation and path resolution logic.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-22 Directory Traversal and the broader category of path traversal attacks within the Common Weakness Enumeration framework. When a remote attacker sends a request containing a URI with %2e%2e sequences, the server processes these paths without adequate validation, allowing the attacker to traverse up the directory hierarchy and access files that should remain protected. The attack vector specifically targets the URI parsing component of the HTTP server implementation, where encoded sequences are not properly decoded and validated before path resolution occurs. This creates a scenario where legitimate file access controls can be bypassed through manipulation of the URI structure, potentially exposing sensitive information such as configuration files, source code, system credentials, or other confidential data stored on the server.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable more sophisticated attack chains that align with multiple tactics described in the MITRE ATT&CK framework. An attacker who successfully exploits this vulnerability can potentially gain access to system files, application configuration details, and sensitive data that may lead to further compromise of the affected system. The vulnerability affects any application that relies on libsoup for HTTP server functionality, which includes numerous web applications, network services, and proxy implementations. The consequences can range from unauthorized data access and information leakage to potential privilege escalation if the application has elevated permissions, as the attacker can potentially read files that contain authentication tokens, database connection strings, or other critical system information. Organizations running vulnerable versions of libsoup are at risk of unauthorized access to their file systems, particularly when the web server has access to directories containing sensitive information.
Mitigation strategies for CVE-2011-2524 focus primarily on upgrading to libsoup version 2.35.4 or later, where the directory traversal vulnerability has been addressed through improved URI parsing and path validation mechanisms. System administrators should implement comprehensive patch management procedures to ensure all affected applications are updated promptly, as this vulnerability has been widely exploited in the wild. Additional protective measures include implementing proper input validation at multiple layers of the application architecture, configuring web servers to restrict file access permissions, and deploying web application firewalls that can detect and block suspicious URI patterns. The vulnerability demonstrates the importance of proper path sanitization and the principle of least privilege in system design, where applications should never be granted unnecessary file system access rights. Security monitoring should include detection of unusual URI patterns containing encoded directory traversal sequences, and organizations should conduct regular vulnerability assessments to identify and remediate similar weaknesses in their software dependencies. The fix implemented in the patched version likely involved strengthening the URI parsing logic to properly decode and validate directory traversal sequences before path resolution occurs, preventing the bypass of intended access controls.