CVE-2018-11695 in LibSaas
Summary
by MITRE
An issue was discovered in LibSaas through 3.5.2. A NULL pointer dereference was found in the function Sass::Expand::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-2018-11695 represents a critical null pointer dereference flaw within the LibSass library version 3.5.2 and earlier. This issue manifests within the Sass::Expand::operator function, which forms a core component of the library's processing pipeline for sass/scss stylesheet compilation. The vulnerability stems from inadequate input validation and error handling mechanisms that fail to properly check for null pointer conditions during the expansion phase of sass expression evaluation. When maliciously crafted sass code is processed through this function, the library attempts to dereference a null pointer, leading to immediate application termination and denial of service conditions.
The technical exploitation of this vulnerability occurs during the parsing and compilation of sass/scss files where the Sass::Expand::operator function receives malformed input that results in a null pointer being accessed. This particular flaw falls under CWE-476 which specifically addresses null pointer dereference conditions in software implementations. The vulnerability is particularly concerning because it can be triggered through normal library usage patterns when processing user-supplied sass content, making it an attractive target for attackers seeking to disrupt services that depend on LibSass for stylesheet compilation. The denial of service impact is immediate and deterministic, as the application crashes upon encountering the null pointer dereference condition.
From an operational perspective, this vulnerability creates significant risk for web applications and services that utilize LibSass for dynamic stylesheet compilation. Systems relying on this library for generating css from sass files become susceptible to denial of service attacks, potentially affecting entire user-facing applications or development environments. The vulnerability can be exploited through various attack vectors including user upload functionality, dynamic template rendering, or any scenario where external sass content is processed. The potential for unspecified other impacts exists because the null pointer dereference could potentially be leveraged in more sophisticated attacks if the library is used in contexts where additional memory corruption might occur, though the primary impact remains denial of service.
Organizations should prioritize immediate patching of affected LibSass versions to address this vulnerability. The recommended mitigation strategy involves upgrading to LibSass version 3.5.3 or later where the null pointer dereference has been resolved through enhanced input validation and proper pointer checking mechanisms. Security teams should also implement additional defensive measures including input sanitization for any sass content processed through the library, rate limiting for stylesheet compilation requests, and monitoring for unusual application crash patterns. This vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and represents a classic example of how input validation failures in widely-used libraries can create systemic security risks across dependent applications and services.