CVE-2018-11499 in LibSass
Summary
by MITRE
A use-after-free vulnerability exists in handle_error() in sass_context.cpp in LibSass 3.4.x and 3.5.x through 3.5.4 that could be leveraged to cause a denial of service (application crash) or possibly unspecified other impact.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 03/17/2023
The vulnerability identified as CVE-2018-11499 represents a critical use-after-free flaw within the LibSass library, specifically within the handle_error() function located in sass_context.cpp. This issue affects versions 3.4.x and 3.5.x through 3.5.4, making it a widespread concern for applications that rely on this popular Sass compiler library. The vulnerability stems from improper memory management practices where a pointer is accessed after the memory it references has been freed, creating a dangerous state that can be exploited by malicious actors.
The technical implementation of this flaw occurs during error handling within the Sass compilation process, where the handle_error() function fails to properly manage memory references when processing malformed input or exceptional conditions. When an error occurs during Sass processing, the function attempts to access memory that has already been deallocated, leading to undefined behavior that can manifest as application crashes or potentially more severe consequences. This type of vulnerability falls under CWE-416, which specifically addresses the use of freed memory, and represents a classic example of memory safety issues that plague C and C++ applications.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can potentially be leveraged to execute arbitrary code or cause system instability. Applications that process untrusted Sass input, such as web applications, content management systems, or build tools that utilize LibSass, become vulnerable to exploitation. The vulnerability is particularly concerning in server-side environments where Sass compilation occurs dynamically, as attackers could craft malicious Sass code to trigger the use-after-free condition and potentially gain unauthorized access to systems. This aligns with ATT&CK technique T1203, which involves gaining access through exploitation of software vulnerabilities, and represents a significant threat vector for systems processing user-supplied content.
Mitigation strategies for CVE-2018-11499 should prioritize immediate patching of affected LibSass versions to 3.5.5 or later, where the memory management issues have been resolved through proper pointer handling and memory deallocation practices. Organizations should also implement input validation and sanitization measures to prevent malformed Sass code from reaching the compilation layer, along with regular security assessments of their Sass processing pipelines. Additionally, maintaining up-to-date dependencies and implementing proper error handling mechanisms can help reduce the attack surface and prevent exploitation of similar memory safety issues within the broader software ecosystem.