CVE-2017-8834 in lobroco
Summary
by MITRE
The cr_tknzr_parse_comment function in cr-tknzr.c in libcroco 0.6.12 allows remote attackers to cause a denial of service (memory allocation error) via a crafted CSS file.
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Analysis
by VulDB Data Team • 10/16/2019
The vulnerability identified as CVE-2017-8834 resides within the cr_tknzr_parse_comment function of libcroco version 0.6.12, a library responsible for parsing Cascading Style Sheets in various applications. This flaw represents a classic memory allocation error that can be exploited remotely through maliciously crafted CSS content, fundamentally undermining the stability and availability of systems that rely on this parsing library. The issue manifests when the parser encounters specially constructed comment sections within CSS files, triggering unexpected memory handling behaviors that lead to system resource exhaustion or application crashes.
The technical exploitation of this vulnerability involves crafting CSS files containing malformed comment structures that cause the cr_tknzr_parse_comment function to allocate excessive memory or enter infinite loops during parsing operations. This memory allocation error stems from inadequate input validation and boundary checking within the comment parsing logic, where the parser fails to properly handle edge cases in comment syntax or malformed nested structures. The vulnerability operates at the parsing layer of CSS processing, making it particularly dangerous as it can be triggered through any application that utilizes libcroco for CSS rendering or processing, including web browsers, content management systems, and desktop applications.
From an operational impact perspective, this vulnerability creates significant risk for systems that process external CSS content, particularly web applications that accept user-generated stylesheets or content management platforms that allow CSS customization. The denial of service condition can result in complete application unavailability, requiring system restarts and potentially allowing attackers to disrupt services for extended periods. This vulnerability aligns with CWE-129, which addresses improper validation of length of input buffers, and represents a memory allocation error that can be leveraged for resource exhaustion attacks. The impact extends beyond simple service disruption as it can potentially be chained with other vulnerabilities to create more sophisticated attack vectors.
Organizations utilizing libcroco 0.6.12 should implement immediate mitigation strategies including upgrading to patched versions of the library, implementing input validation for CSS content, and deploying network segmentation to limit exposure. The ATT&CK framework categorizes this vulnerability under T1499.004, which covers network denial of service attacks, and T1059.001 for command and scripting interpreter techniques that may be used to exploit the service disruption. System administrators should also consider implementing monitoring solutions that detect unusual memory allocation patterns or parsing errors that could indicate exploitation attempts, as the vulnerability creates predictable failure patterns that can be monitored for defensive purposes.