Angular platform-server
CVE-2026-101895
HIGH
GHSA-f67j-2jqw-jpq7
Severity by source
Trivial static payload sent remotely with no auth or interaction (AV:N/AC:L/PR:N/UI:N); pure event-loop-freezing DoS gives A:H with C:N/I:N.
Estimated by vuln.today — no official severity rating has been published for this CVE yet.
Lifecycle Timeline
5DescriptionCVE.org
A Denial of Service (DoS) vulnerability exists in @angular/platform-server's DOM emulation parser (domino). When processing untrusted user input containing an incomplete DOCTYPE declaration ending with whitespace before EOF (such as <!DOCTYPE html ), the HTML parser enters an infinite synchronous loop, pegging CPU utilization at 100% and completely freezing the Node.js server process.
Technical Description
In Angular Server-Side Rendering (SSR), @angular/platform-server uses domino to parse and sanitize HTML bound through template bindings (such as [innerHTML]) or manipulated via DOM APIs.
In Domino's HTML parser (lib/HTMLParser.js), tokenizer states that specify fixed lookahead-such as after_doctype_name_state (lookahead = 6)-rely on the state handler function to explicitly advance the character index pointer (nextchar). While branches for whitespace, >, and keyword matching advance nextchar, the EOF branch (case -1: // EOF) emitted doctype and EOF tokens without advancing nextchar or transitioning out of the state:
case -1: // EOF
forcequirks();
emitDoctype();
emitEOF();
break;Because nextchar remained unchanged pointing to the EOF marker character (\uFFFF), the scanner loop (while (nextchar < numchars)) repeatedly re-invoked after_doctype_name_state with codepoint = EOF indefinitely. In Node.js's single-threaded runtime, this synchronous loop starves the event loop entirely.
Impact & Reachability
- Reachability: The vulnerability is reachable in any Angular SSR application where untrusted user input is bound to
[innerHTML], interpolated into markup, or sanitized on the server. - Impact: Successful exploitation allows an unauthenticated remote attacker to cause an immediate Denial of Service (DoS) by sending a payload containing an incomplete DOCTYPE (e.g.,
<!DOCTYPE html). The Node.js SSR process locks up at 100% CPU and ceases responding to all concurrent and subsequent HTTP requests.
Proof of Concept:
import { Component } from '@angular/core';
@Component({
selector: 'app-root',
standalone: true,
template: `<div [innerHTML]="payload"></div>`,
})
export class AppComponent {
// Attacker-controlled input containing an incomplete DOCTYPE ending with whitespace
payload = '<!DOCTYPE html ';
}Workarounds
- Avoid binding untrusted user input directly to
[innerHTML]in server-rendered templates; use standard text interpolation ({{ userInput }}) or[textContent]when raw HTML rendering is not required. - Validate or sanitize user input before passing it to
[innerHTML]on the server by stripping or rejecting strings matching/^<!DOCTYPE/i.
Articles & Coverage 1
AnalysisAI
Server-side rendering in Angular (the npm package @angular/platform-server, which embeds the Domino DOM emulation parser) can be driven into an infinite synchronous loop that pins a CPU core at 100% and freezes the entire Node.js SSR process, denying service to all concurrent and subsequent requests. The trigger is a single, trivially crafted input - an incomplete DOCTYPE declaration ending in whitespace at end-of-input, such as <!DOCTYPE html - supplied wherever untrusted content reaches server-side HTML parsing, most commonly via an [innerHTML] binding. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires an Angular Server-Side Rendering application built on @angular/platform-server (vulnerable ranges: <=19.2.25, 20.0.0-20.3.30, 21.0.0-21.2.22, 22.0.0-22.1.5) that routes untrusted, attacker-controlled input into server-side HTML parsing - specifically binding it to `[innerHTML]`, interpolating it into rendered markup, or sanitizing it on the server via Domino. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | No CVSS was supplied by the source, so all severity signals below are inferred from the description. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Vendor-released patches are available: upgrade @angular/platform-server to 22.1.6 (from 22.0.0-22.1.5), 21.2.23 (from 21.0.0-21.2.22) or 20.3.31 (from 20.0.0-20.3.30) as appropriate for your Angular major line, as documented in GHSA-f67j-2jqw-jpq7 (https://github.com/angular/angular/security/advisories/GHSA-f67j-2jqw-jpq7). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all applications using @angular/platform-server versions <=19.2.25, 20.0.0-20.3.30, 21.0.0-21.2.22, and 22.0.0-22.1.5; disable server-side rendering if feasible, or apply strict input validation to reject malformed DOCTYPE declarations (e.g., incomplete DOCTYPE ending in whitespace) in any untrusted content reaching [innerHTML] bindings; deploy WAF rules to block such payloads. …
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External POC / Exploit Code
Leaving vuln.today