---
id: CVE-2026-101896
aliases:
  - GHSA-ff3f-86qr-9cv3
title: >-
  Angular Server-Side Rendering (SSR): Denial of Service via Numeric URL Matrix
  Parameters
summary: >-
  Angular Server-Side Rendering (SSR): Denial of Service via Numeric URL Matrix
  Parameters
severity: high
cwe:
  - CWE-400
  - CWE-770
vendor: angular
product: '@angular/router'
ecosystem: npm
affected:
  - '@angular/router >= 22.0.0, < 22.2.0'
  - '@angular/router >= 21.0.0, < 21.2.24'
  - '@angular/router >= 20.0.0, < 20.3.32'
  - '@angular/router <= 19.2.25'
patched:
  - '@angular/router 22.2.0'
  - '@angular/router 21.2.24'
  - '@angular/router 20.3.32'
published: '2026-09-30'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T15:40:48Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-ff3f-86qr-9cv3'
references:
  - url: 'https://github.com/angular/angular/security/advisories/GHSA-ff3f-86qr-9cv3'
  - url: 'https://github.com/angular/angular/issues/70716'
  - url: 'https://github.com/angular/angular/pull/70717'
  - url: >-
      https://github.com/angular/angular/commit/03872a80bcf1c89b2b04cdd3f444b2ee954da583
  - url: >-
      https://github.com/angular/angular/commit/5af61216eab8bf4a6697a1d79bda3d857c06f89d
  - url: >-
      https://github.com/angular/angular/commit/ddfe21072ba32ca4cd9d7d3c6b7df66af81d58c4
  - url: 'https://github.com/advisories/GHSA-ff3f-86qr-9cv3'
tags:
  - ghsa
  - npm
ingestedAt: '2026-09-30T16:10:06.871Z'
---

## Overview

A denial of service (DoS) vulnerability was identified in `@angular/router` when Server-Side Rendering (SSR) is enabled on Node.js (V8).

When `@angular/router` parses incoming request URLs, it extracts path segments, matrix parameters, and child outlets into plain JavaScript objects (`Record<string, string>`). When matrix parameter names or outlet names are numeric strings (such as `/a;990;2522`), the V8 JavaScript engine interprets them as array-indexed properties rather than named properties.

Under V8's internal property-storage heuristics, setting numeric keys on an initially empty object causes V8 to allocate a dense array backing store (`HOLEY_ELEMENTS`) sized to the maximum index rather than falling back to sparse dictionary storage. Specifically, assigning sequential or moderately large numeric keys (like `990` followed by `2522`) causes V8 to allocate a contiguous backing store of ~2,522 pointers (~20 KB to 25 KB of heap) for a single 11-byte segment.

Because each segment in a URL path allocates its own independent `parameters` object, an attacker can craft URLs with repeated numeric matrix parameters to achieve an asymmetric memory amplification factor of approximately **~350x**.

### Impact

Successful exploitation allows an unauthenticated remote attacker to exhaust the Node.js old-space heap with modest request volume, terminating the SSR worker with an unrecoverable `JavaScript heap out of memory` fatal error and causing a Denial of Service.

* **High Amplification:** A single 11-byte segment (`/a;990;2522`) consumes ~20 KB–25 KB of V8 heap.
* **Low Concurrency Required:**
  * With 8 KB request paths (~740 segments, within default Nginx 8 KB buffer limits), as few as **12–22 concurrent requests** crash a 256 MiB–512 MiB Node.js SSR worker.
  * With smaller 1 KB–2 KB request paths (~90–180 segments), a burst of ~50–100 concurrent requests achieves the same heap exhaustion.
* **Client-side SPAs Unaffected:** Pure client-side Angular applications (Single Page Applications without SSR) are **not** vulnerable, as local browser memory consumption does not cross a security boundary.

### Attack Preconditions & Vulnerable Configurations

An application is affected only if **all** of the following conditions are met:

* **SSR Enabled:** The application runs in a Server-Side Rendering environment powered by Node.js / V8.
* **Direct Router Parsing:** User-controlled request URLs are parsed by `@angular/router` during SSR.
* **No Reverse-Proxy Semicolon/Segment Filtering:** Upstream reverse proxies (Nginx, Cloudflare, ALB) forward URLs containing semicolons (`;`) and multiple path segments without stripping or rejecting them.

#### Exploit Payload Example

An attacker sends concurrent HTTP requests with repeated numeric matrix parameters:

```http
GET /a;990;2522/a;990;2522/a;990;2522/... HTTP/1.1
Host: example.com
```

Even with paths under 2 KB, overlapping requests during SSR will rapidly consume the V8 heap until the process crashes.

### Patches

The issue is resolved by updating `@angular/router` to enforce V8 dictionary elements storage (`setUrlDerivedKey`) for numeric URL-derived keys (index >= 32). This prevents V8 from allocating oversized contiguous array backing stores while preserving route matching, parameter values, and component input bindings.

* `22.2.0`
* `21.2.24`
* `20.3.32`

### Workarounds & Mitigations

If you cannot immediately upgrade to a patched version, apply one of the following mitigations at your edge or reverse proxy:

1. **Block or Sanitize Matrix Parameters at the Reverse Proxy:**  
   Configure your reverse proxy (e.g., Nginx, Cloudflare, or AWS WAF) to reject or strip semicolons (`;`) in request paths before forwarding requests to the Angular SSR service:
   ```nginx
   # Nginx example: reject requests containing matrix parameters
   if ($uri ~* ";") {
       return 400;
   }
   ```
2. **Enforce Strict Path Segment Limits:**  
   Reject requests with excessive path depth (e.g., more than 20–30 segments).
3. **Increase Node.js Old Space:**  
   Increase `--max-old-space-size` (e.g., to 2048 or 4096 MB) to increase the concurrency threshold required to exhaust memory, though this does not fully eliminate the vulnerability under sustained traffic.

## Affected packages

- `@angular/router >= 22.0.0, < 22.2.0`
- `@angular/router >= 21.0.0, < 21.2.24`
- `@angular/router >= 20.0.0, < 20.3.32`
- `@angular/router <= 19.2.25`

## Remediation

Upgrade to a patched release:

- `@angular/router 22.2.0`
- `@angular/router 21.2.24`
- `@angular/router 20.3.32`