CVE-2018-20190 in LibSass
Summary
by MITRE
In LibSass 3.5.5, a NULL Pointer Dereference in the function Sass::Eval::operator()(Sass::Supports_Operator*) in eval.cpp may cause a Denial of Service (application crash) via a crafted sass input file.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2018-20190 represents a critical NULL pointer dereference flaw within LibSass version 3.5.5, a widely used C++ library for compiling Sass stylesheet files into CSS. This vulnerability specifically affects the Sass::Eval::operator() function within the eval.cpp source file, where improper input validation leads to application instability. The flaw manifests when processing crafted sass input files that contain malformed syntax structures, causing the evaluation engine to attempt dereferencing a null pointer during the compilation process. This type of vulnerability falls under CWE-476 which categorizes NULL pointer dereference issues, representing a fundamental programming error that can lead to abrupt application termination.
The operational impact of this vulnerability extends beyond simple application crashes, as it creates a reliable denial of service condition that attackers can exploit systematically. When a maliciously crafted sass file is processed by any application utilizing LibSass 3.5.5, the evaluation engine encounters a null pointer reference during the Supports_Operator processing phase, resulting in an immediate segmentation fault or access violation. This behavior aligns with ATT&CK technique T1499.004 which describes the use of resource exhaustion attacks through application crashes and denial of service conditions. The vulnerability affects any system that relies on LibSass for stylesheet compilation, including web applications, build systems, and static site generators that process user-provided sass content.
Mitigation strategies for CVE-2018-20190 require immediate version updates to LibSass 3.5.6 or later, where the NULL pointer dereference has been resolved through proper input validation and null checks within the evaluation engine. Organizations should implement comprehensive input sanitization measures for any sass content processing pipelines, particularly when handling user-generated content or external inputs. Security teams should also consider implementing runtime protections such as address space layout randomization and stack canaries to mitigate potential exploitation attempts. Additionally, the vulnerability demonstrates the importance of thorough testing in compiler and evaluation engine components, as the flaw could be leveraged in broader attack chains targeting web applications that utilize sass compilation as part of their build processes, making it essential for developers to adopt secure coding practices and regular dependency updates to prevent similar issues in other components of their software stack.