CVE-2018-20801 in Highcharts JS
Summary
by MITRE
In js/parts/SvgRenderer.js in Highcharts JS before 6.1.0, the use of backtracking regular expressions permitted an attacker to conduct a denial of service attack against the SVGRenderer component, aka ReDoS.
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2018-20801 resides within the Highcharts JavaScript library, specifically in the SvgRenderer.js file which handles SVG rendering operations. This issue affects versions prior to 6.1.0 and represents a classic example of a Regular Expression Denial of Service (ReDoS) vulnerability that can be exploited to disrupt system availability. The flaw manifests when the SVGRenderer component processes user-provided input through backtracking regular expressions, creating a potential attack surface where malicious input can cause excessive CPU consumption and system resource exhaustion.
The technical implementation of this vulnerability stems from the use of inefficient regular expressions that exhibit exponential backtracking behavior when processing carefully crafted malicious input strings. When an attacker provides input that matches the pattern of these vulnerable regular expressions, the JavaScript engine must perform an exponential number of operations to determine whether the input matches the pattern, leading to significant performance degradation or complete system hang. This behavior directly aligns with CWE-400, which classifies excessive computation as a vulnerability, and more specifically maps to CWE-1321 which addresses regular expression vulnerabilities.
The operational impact of CVE-2018-20801 extends beyond simple performance degradation to potentially enable complete denial of service conditions within applications that utilize Highcharts for data visualization. Attackers can exploit this vulnerability by crafting input strings that trigger the problematic regular expressions during SVG rendering operations, causing web applications to become unresponsive or crash entirely. This vulnerability is particularly concerning in web applications where user input is directly rendered through the SVG renderer component, as it allows attackers to target the core rendering functionality without requiring complex exploitation techniques. The attack vector typically involves sending malicious data through API endpoints or user interfaces that eventually pass input to the vulnerable SVG rendering code path.
Mitigation strategies for CVE-2018-20801 primarily involve upgrading to Highcharts version 6.1.0 or later, which contains the patched implementation that eliminates the vulnerable regular expressions. Organizations should also implement proper input validation and sanitization measures at application boundaries to reduce the risk of malicious input reaching the vulnerable code paths. Additionally, implementing rate limiting and resource monitoring can help detect and prevent exploitation attempts before they cause significant impact. From an ATT&CK framework perspective, this vulnerability maps to T1499.004 which covers network denial of service attacks, and T1595.001 which addresses reconnaissance through active scanning. Security teams should also consider implementing web application firewalls and intrusion detection systems that can identify and block suspicious input patterns associated with ReDoS attacks. The remediation process should include thorough testing of the upgraded library to ensure that all SVG rendering functionality continues to operate correctly while eliminating the vulnerable regular expression patterns that enabled the attack.