CVE-2018-11697 in LibSaas
Summary
by MITRE
An issue was discovered in LibSaas through 3.5.4. An out-of-bounds read of a memory region was found in the function Sass::Prelexer::exactly() which could be leveraged by an attacker to disclose information or manipulated to read from unmapped memory causing a denial of service.
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Analysis
by VulDB Data Team • 03/21/2023
The vulnerability CVE-2018-11697 represents a critical out-of-bounds read flaw in the LibSass library version 3.5.4 and earlier, which serves as a fundamental component in the Sass stylesheet language processing ecosystem. This memory safety issue exists within the Sass::Prelexer::exactly() function, a core parsing routine responsible for pattern matching and lexical analysis during Sass compilation processes. The flaw arises from inadequate bounds checking when processing input data, creating a scenario where the application attempts to access memory locations beyond the allocated buffer boundaries. This particular vulnerability falls under the CWE-125 weakness category, which specifically addresses out-of-bounds read conditions that can lead to information disclosure or system instability.
The technical exploitation of this vulnerability occurs when LibSass processes malformed or specially crafted Sass input files that trigger the vulnerable prelexer function. During the parsing phase, the Sass::Prelexer::exactly() function fails to properly validate input boundaries, allowing an attacker to craft input sequences that cause the parser to read memory locations that are either unmapped or contain sensitive data. This behavior can manifest in two primary ways: information disclosure where adjacent memory contents are read and potentially exposed to attackers, or denial of service through segmentation faults when attempting to access unmapped memory regions. The vulnerability's impact is particularly concerning because LibSass is widely used across numerous web applications and development environments, making it a prime target for exploitation.
From an operational standpoint, this vulnerability creates significant risks for organizations relying on Sass processing capabilities, as it can be leveraged in both offensive and defensive attack scenarios. The information disclosure aspect poses a serious threat to system security, as attackers could potentially extract sensitive data from memory locations, including cryptographic keys, user credentials, or application logic that might reveal internal system structures. The denial of service component further compounds the risk by enabling attackers to disrupt services through carefully crafted input that causes application crashes or hangs. This vulnerability aligns with ATT&CK technique T1059.001 for command and control through potential information gathering activities, and represents a classic example of how memory safety issues in parsing libraries can create widespread security implications.
Mitigation strategies for CVE-2018-11697 should prioritize immediate patching of affected LibSass versions to 3.5.5 or later, where the out-of-bounds read has been corrected through proper input validation and bounds checking mechanisms. Organizations should implement comprehensive input sanitization measures for any Sass processing workflows, particularly when handling untrusted input from external sources. Additionally, deployment of runtime protections such as address space layout randomization and stack canaries can help mitigate exploitation attempts, though these are not complete solutions. Security monitoring should include detection of unusual parsing behavior or memory access patterns that might indicate exploitation attempts, while regular security assessments of Sass-dependent applications can help identify potential attack vectors. The fix implemented in newer versions typically involves strengthening the input validation within the Sass::Prelexer::exactly() function to ensure proper boundary checks before any memory access operations occur, addressing the root cause of the vulnerability through defensive programming practices.