CVE-2018-6341 in React
Summary
by MITRE
React applications which rendered to HTML using the ReactDOMServer API were not escaping user-supplied attribute names at render-time. That lack of escaping could lead to a cross-site scripting vulnerability. This issue affected minor releases 16.0.x, 16.1.x, 16.2.x, 16.3.x, and 16.4.x. It was fixed in 16.0.1, 16.1.2, 16.2.1, 16.3.3, and 16.4.2.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability described in CVE-2018-6341 represents a critical cross-site scripting flaw in React applications that utilize the ReactDOMServer API for server-side rendering. This issue specifically targeted the rendering process where user-supplied attribute names were not being properly escaped, creating a pathway for malicious input to be executed as JavaScript code within the browser context. The vulnerability affected a broad range of React versions including 16.0.x through 16.4.x, indicating it was a widespread concern that impacted numerous applications relying on server-side rendering capabilities. The flaw occurred during the HTML generation phase rather than client-side execution, making it particularly dangerous as it could be exploited even before the application code reached the user's browser.
The technical root cause of this vulnerability stems from insufficient input validation and sanitization during the server-side rendering process. When ReactDOMServer encountered user-provided attribute names in the component structure, it failed to properly escape special characters that could be interpreted as HTML or JavaScript code. This lack of proper escaping created an injection point where malicious actors could craft attribute names containing script tags or other harmful content that would be rendered directly into the HTML output. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and demonstrates how improper handling of untrusted data during rendering operations can lead to severe security consequences. Attackers could exploit this by submitting crafted attribute names that would be rendered without proper sanitization, allowing malicious scripts to execute in the context of other users' browsers.
The operational impact of CVE-2018-6341 was significant for organizations running React applications that utilized server-side rendering. Applications vulnerable to this flaw could be exploited to perform session hijacking, steal user credentials, deface websites, or redirect users to malicious sites. The vulnerability was particularly concerning because it affected multiple minor releases, suggesting that many production applications might have been running without adequate protection. The fact that the issue was present in versions 16.0.1 through 16.4.2 meant that organizations needed to carefully audit their React dependencies and ensure proper version updates were implemented across their application infrastructure. This vulnerability also highlighted the importance of proper input sanitization in server-side rendering contexts, as the issue could be exploited even when client-side security measures were in place.
Mitigation strategies for CVE-2018-6341 centered on updating React to the patched versions mentioned in the advisory, specifically 16.0.1, 16.1.2, 16.2.1, 16.3.3, and 16.4.2. Organizations should have implemented comprehensive dependency management practices to ensure all React components were updated to versions that included the necessary escaping mechanisms. Additionally, security teams should have considered implementing additional input validation layers at the application level, even when using patched versions, to provide defense-in-depth. The vulnerability also reinforced the importance of following secure coding practices for server-side rendering, including implementing proper HTML escaping for all user-provided content and establishing automated security scanning processes for dependency updates. Organizations should have reviewed their deployment pipelines to ensure that security patches were applied promptly and consistently across all environments. This incident demonstrated how vulnerabilities in core libraries could have cascading effects throughout the web application ecosystem, emphasizing the need for continuous security monitoring and proactive patch management strategies that align with ATT&CK framework concepts for defensive measures against code injection attacks.