Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.31, 21.2.23, and 22.1.6, the @angular/platform-server DOM emulation parser can enter an infinite synchronous loop when Angular server-side rendering processes attacker-controlled HTML containing an incomplete DOCTYPE that ends with whitespace at end of input. In Domino lib/HTMLParser.js, after_doctype_name_state emits doctype and EOF tokens without advancing nextchar or leaving the fixed-lookahead state, so the scanner repeatedly handles the same EOF marker. A remote unauthenticated attacker can use this condition through server-side HTML parsing paths such as innerHTML binding to consume a Node.js SSR worker at full CPU, starve the event loop, and stop concurrent and subsequent requests. This issue is fixed in versions 20.3.31, 21.2.23, and 22.1.6.
Weakness
The product does not properly control the allocation and maintenance of a limited resource.
Potential Mitigations
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/147.html
- https://cwe.mitre.org/data/definitions/227.html
- https://cwe.mitre.org/data/definitions/492.html
References
- https://github.com/angular/angular/commit/3db26e2544964d07a520836ad01f02f36ec88e25
- https://github.com/angular/angular/commit/fc2e8fbc0bda2f5c11585e8a0cbd88c074f5e567
- https://github.com/angular/angular/releases/tag/v20.3.31
- https://github.com/angular/angular/releases/tag/v21.2.23
- https://github.com/angular/angular/releases/tag/v22.1.6
- https://github.com/angular/angular/security/advisories/GHSA-f67j-2jqw-jpq7
- https://github.com/angular/domino/commit/4d97473116d000e3fd4d6f75ec98cbd67576fa6f
- https://github.com/angular/angular/security/advisories/GHSA-f67j-2jqw-jpq7