CVE-2018-8768 in Notebook
Summary
by MITRE
In Jupyter Notebook before 5.4.1, a maliciously forged notebook file can bypass sanitization to execute JavaScript in the notebook context. Specifically, invalid HTML is 'fixed' by jQuery after sanitization, making it dangerous.
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Analysis
by VulDB Data Team • 02/22/2023
The vulnerability identified as CVE-2018-8768 represents a critical security flaw in Jupyter Notebook versions prior to 5.4.1 that undermines the application's HTML sanitization mechanisms. This issue arises from the improper handling of malformed HTML content within notebook files, creating a pathway for malicious actors to execute arbitrary JavaScript code within the notebook environment. The vulnerability specifically targets the notebook's rendering pipeline where HTML content is processed and displayed to users, making it particularly dangerous in collaborative environments where multiple users may interact with shared notebooks.
The technical root cause of this vulnerability stems from the interaction between the HTML sanitization process and jQuery's automatic HTML correction features. When Jupyter Notebook processes notebook files containing maliciously crafted HTML content, the sanitization library removes potentially dangerous elements but fails to account for jQuery's behavior of automatically repairing malformed HTML structures. This repair process reintroduces previously sanitized dangerous elements into the document, effectively bypassing the security controls designed to prevent cross-site scripting attacks. The vulnerability is classified as a CWE-79 Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly sanitize user input that could lead to XSS attacks. This flaw demonstrates the complexity of HTML sanitization in web applications and the potential for seemingly benign HTML correction mechanisms to undermine security controls.
The operational impact of CVE-2018-8768 extends beyond simple code execution, as it can enable attackers to perform a wide range of malicious activities within the notebook context. An attacker could craft a malicious notebook file that appears legitimate but contains hidden JavaScript payloads designed to steal user credentials, access sensitive data, or establish persistent access to the system. The vulnerability is particularly concerning in enterprise environments where Jupyter Notebooks are used for data analysis and collaborative research, as it allows for the compromise of entire notebook sessions and potentially the underlying systems. The attack vector is particularly insidious because it leverages the trust users place in notebook files, making it difficult to distinguish between legitimate and malicious content without proper validation mechanisms.
Organizations and users affected by this vulnerability should immediately upgrade to Jupyter Notebook version 5.4.1 or later, which includes fixed sanitization logic that properly handles malformed HTML content. The mitigation strategy should also include implementing additional security measures such as network segmentation, access controls, and regular security audits of notebook files. Security teams should also consider implementing content security policies and monitoring for suspicious notebook file modifications. This vulnerability aligns with ATT&CK technique T1059.001 Command and Scripting Interpreter, as it enables attackers to execute code within the notebook environment. Additionally, the issue demonstrates the importance of understanding how different libraries interact in security contexts, as the vulnerability emerged from the unexpected interaction between sanitization and HTML correction libraries rather than from a direct implementation flaw in the primary security controls.