Infinite Loop Vulnerability in Angular.js DOM Parser
Summary
DEBIAN-CVE-2026-101895: Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Affects angular.js versions 1.8.3-1 – 1.8.3-3. No fix is published. How to fix ↓
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Background
Angular is a robust development platform designed for building mobile and desktop web applications using TypeScript, JavaScript, and other languages. It provides a comprehensive framework for creating dynamic single-page applications and is widely used for its modular architecture and powerful features. However, prior to versions 20.3.31, 21.2.23, and 22.1.6, Angular's @angular/platform-server DOM emulation parser was susceptible to a critical vulnerability that could lead to performance degradation under certain conditions.
Vulnerability Detail
The vulnerability arises from an infinite synchronous loop in the DOM emulation parser of Angular's server-side rendering. When processing attacker-controlled HTML with an incomplete DOCTYPE that ends with whitespace, the parser can enter a state where it continuously handles the same EOF marker without advancing, leading to high CPU consumption. This can starve the Node.js event loop, preventing it from handling concurrent and subsequent requests, effectively causing a denial of service. The issue is rooted in the HTMLParser.js file, specifically within the after_doctype_name_state function.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, developers can sanitize or validate the HTML content being processed to ensure that it does not contain incomplete DOCTYPE declarations, thereby preventing the parser from entering the infinite loop state.
Conclusion
The infinite loop vulnerability in Angular.js's DOM parser poses a significant risk to applications using affected versions. By updating to the latest patched versions, developers can mitigate this risk effectively. Additionally, utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
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FAQ
Versions prior to 20.3.31, 21.2.23, and 22.1.6 are affected by this vulnerability.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
A remote unauthenticated attacker can exploit this vulnerability to consume CPU resources, leading to denial of service by starving the event loop.
Yes, updating to the patched versions of Angular.js (20.3.31, 21.2.23, or 22.1.6) resolves the issue.
Implement input validation or sanitization to prevent the parser from processing incomplete DOCTYPE declarations as a temporary measure.
References
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