CVE-2019-12136 in Boostnote
Summary
by MITRE
There is XSS in BoostIO Boostnote 0.11.15 via a label named mermaid, as demonstrated by a crafted SRC attribute of an IFRAME element.
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Analysis
by VulDB Data Team • 09/21/2023
The vulnerability CVE-2019-12136 represents a cross-site scripting flaw discovered in BoostIO Boostnote version 0.11.15 that specifically exploits the handling of mermaid labels within the application's rendering process. This vulnerability manifests when a malicious user crafts a specially designed iframe element with a SRC attribute that contains malicious script code, which then gets executed in the context of other users who view the compromised note. The issue stems from insufficient input validation and sanitization of user-provided content, particularly in how the application processes mermaid diagram labels that are embedded within markdown notes. The vulnerability allows an attacker to inject malicious JavaScript code that can be executed in the browser of other users who access the affected note, potentially leading to session hijacking, data theft, or further exploitation of the victim's browser environment.
The technical implementation of this vulnerability involves the application's failure to properly sanitize or escape user input when processing mermaid diagram labels within markdown documents. When Boostnote renders notes containing mermaid syntax, it processes the label content without adequate protection against malicious script injection. The specific exploitation occurs through the SRC attribute of iframe elements that are embedded within the mermaid label processing logic, where the application does not validate or sanitize the source URL before rendering it in the browser context. This represents a classic case of insufficient output escaping and improper input validation, which are fundamental security weaknesses that have been consistently identified as critical vulnerabilities in web applications. The vulnerability aligns with CWE-79, which specifically addresses Cross-site Scripting flaws, and demonstrates the importance of proper input sanitization in web applications. The attack vector leverages the application's legitimate rendering capabilities to execute malicious code, making it particularly dangerous as it can bypass traditional security controls that might not detect the injection within legitimate-looking markdown content.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable sophisticated attack scenarios that compromise user sessions and data integrity. An attacker could craft malicious notes containing iframe elements that redirect users to phishing sites, steal session cookies, or execute additional malicious payloads that exploit other browser vulnerabilities. The vulnerability affects all users who view compromised notes, making it particularly dangerous in collaborative environments where multiple users share and access the same documents. The exploitation requires minimal technical knowledge and can be automated, making it an attractive target for threat actors. From an attacker's perspective, this vulnerability provides a persistent attack surface that can be leveraged for prolonged access to victim systems, potentially leading to data exfiltration or lateral movement within network environments. The impact is particularly severe in enterprise environments where Boostnote might be used for documentation sharing, as compromised notes could affect numerous users simultaneously. The vulnerability also demonstrates the broader challenge of securing rich text editing environments where users can embed various content types, including HTML and iframe elements, without proper sanitization.
The recommended mitigations for CVE-2019-12136 involve implementing comprehensive input validation and output sanitization measures within the Boostnote application. The primary fix should include proper escaping of all user-provided content, particularly when processing mermaid labels and other embedded content types. The application should implement a whitelist-based approach for iframe source validation, rejecting any external sources that do not conform to predefined safe patterns. Additionally, the application should implement Content Security Policy headers that restrict the execution of inline scripts and limit the sources from which external content can be loaded. Input sanitization should be applied at multiple levels, including during note creation and rendering phases, to ensure that malicious content cannot be introduced or executed within the application. The development team should also implement proper HTML escaping for all dynamic content and consider implementing a sandboxed rendering environment for potentially dangerous content types. These mitigations align with ATT&CK technique T1203, which covers Exploitation for Credential Access, and T1059, which addresses Command and Scripting Interpreter, by preventing the execution of malicious scripts through the application's legitimate rendering pathways. The vulnerability also highlights the need for regular security assessments of rich text processing components and the importance of implementing automated security scanning tools that can detect similar injection vulnerabilities in application code.