CVE-2018-11696 in LibSaas
Summary
by MITRE
An issue was discovered in LibSaas through 3.5.4. A NULL pointer dereference was found in the function Sass::Inspect::operator which could be leveraged by an attacker to cause a denial of service (application crash) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 03/21/2023
The vulnerability identified as CVE-2018-11696 represents a critical NULL pointer dereference flaw within the LibSass library version 3.5.4 and earlier. This issue resides in the Sass::Inspect::operator function, which is a core component responsible for inspecting and processing Sass stylesheet syntax. The flaw manifests when the library encounters specific input patterns that result in a null pointer being dereferenced during the inspection process, leading to immediate application termination and denial of service conditions.
This vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software systems. The technical implementation of the flaw occurs within the Sass::Inspect::operator function where the code fails to properly validate pointer references before attempting to access memory locations. When malformed or specially crafted input data is processed through the Sass inspection mechanism, the function attempts to dereference a null pointer, causing the application to crash with a segmentation fault or access violation error. The nature of this vulnerability makes it particularly dangerous as it can be triggered through simple input manipulation without requiring complex exploitation techniques.
The operational impact of CVE-2018-11696 extends beyond simple denial of service scenarios, as it can potentially be leveraged for more sophisticated attacks depending on the environment where LibSass is deployed. Applications that rely on LibSass for dynamic stylesheet compilation, including web applications, content management systems, and static site generators, become vulnerable to this attack vector. The vulnerability can be exploited by attackers who submit malicious input to web forms or API endpoints that process Sass content, causing the target application to crash repeatedly and effectively rendering it unavailable to legitimate users. This represents a significant risk for web applications that dynamically compile user-provided Sass content without proper input validation.
From an adversary perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and T1211 which involves exploitation of software vulnerabilities. The attack surface is particularly broad as LibSass is widely used across numerous platforms and frameworks, making it a valuable target for attackers seeking to disrupt services. The vulnerability can be exploited through various means including direct input manipulation, file upload attacks, or even through indirect pathways if the vulnerable library is used as a dependency in larger applications. Organizations using affected versions should immediately consider implementing input validation measures and monitoring for unusual application crashes that might indicate exploitation attempts.
The recommended mitigation strategy involves upgrading to LibSass version 3.5.5 or later, where the NULL pointer dereference has been addressed through proper pointer validation and error handling mechanisms. Additionally, implementing input sanitization measures at the application level can provide defense-in-depth protection against potential exploitation attempts. Organizations should also conduct comprehensive vulnerability assessments to identify all systems and applications that depend on vulnerable versions of LibSass, ensuring that all affected components receive appropriate updates and patches. The vulnerability demonstrates the critical importance of proper memory management and input validation in library code, particularly when dealing with user-supplied data that must be processed through complex parsing and compilation routines.