# CVE-2026-44437: @angular/ssr — Fix Available

📦 npm

Not in CISA KEV

# CVE-2026-44437 — @angular/ssr

[Fix: angular/angular-cli#33031](https://github.com/angular/angular-cli/pull/33031)

CVE-2026-44437 is a Path Traversal vulnerability in @angular/ssr. A fix is available for @angular/ssr — see the affected versions and patch details below.

Angular SSR: Open Redirect and Request Steering via Encoded X-Forwarded-Prefix

Also known as[GHSA-69xr-m8h6-h664](/vulnerability/GHSA-69xr-m8h6-h664)

Published

May 13, 2026

Updated

Oct 28, 2026

Affected

4 pkgs

Patched

4 / 4

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
-   CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44437.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.2%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs10th percentile — riskier than 10% of all scored CVEsHighest risk

0.00%0.27%0.54%0.80%0.0%0.2%Jun 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## Real-World Exposure

4 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

97other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

`@angular/ssr`npm

735Kdownloads / week

## Description

#### Description

A vulnerability exists in the `X-Forwarded-Prefix` header processing logic within Angular SSR. The internal validation mechanism fails to properly account for URL-encoded characters, specifically dots (`%2e%2e`). This allows an attacker to bypass security filters by injecting encoded path traversal sequences that are later decoded and utilized by the application logic. When an Angular SSR application is configured to trust proxy headers and is deployed behind a proxy that forwards the `X-Forwarded-Prefix` header without prior sanitization, an attacker can provide a payload such as `/%2e%2e/evil`.

The vulnerability manifests in two ways:

-   Open Redirect: The application processes a redirect (e.g., router `redirectTo`). The decoded traversal payload manipulates the Location header, forcing the browser to an unintended path or external domain.
-   Server-Side Request Steering: The manipulated prefix is used as the base path for server-side `HttpClient` requests. This causes the server to make requests to unintended internal paths or external endpoints.

#### Attack Preconditions

-   The application must use Angular SSR.
-   The application must perform internal redirects or use relative URLs in server-side `HttpClient` requests.
-   The upstream infrastructure (Reverse Proxy/CDN) must pass the `X-Forwarded-Prefix` header to the SSR process without stripping or sanitizing it.

#### Workarounds

Until the patch is applied, developers should manually sanitize the `X-Forwarded-Prefix` header in their `server.ts`. The workaround involves decoding the component to catch encoded traversal attempts before normalization:

```
app.use((req, res, next) => {
  let prefix = req.headers['x-forwarded-prefix'];
  if (Array.isArray(prefix)) prefix = prefix[0];

  if (prefix) {
    try {
      // Decode the prefix to catch encoded characters like %2e (dots)
      const decodedPrefix = decodeURIComponent(prefix);
      
      // Sanitize: remove traversal attempts and ensure a safe leading slash
      req.headers['x-forwarded-prefix'] = decodedPrefix
        .replace(/\.\./g, '')       // Remove any dot-dot sequences
        .replace(/^[/\\]+/, '/');   // Ensure it starts with exactly one slash
    } catch (e) {
      // If decoding fails, remove the potentially malicious header entirely
      delete req.headers['x-forwarded-prefix'];
    }
  }
  next();
});
```

#### Configuring Trusted Proxy Headers

By default, Angular ignores all X-Forwarded-\* headers. If your application is behind a trusted reverse proxy (like a load balancer) that sets these headers, you can configure Angular to trust them. You can configure trustProxyHeaders when initializing the application engine:

```
const appEngine = new AngularAppEngine({
  // Trust specific headers
  trustProxyHeaders: ['x-forwarded-host', 'x-forwarded-proto', 'x-forwarded-prefix'], 
});

const nodeAppEngine = new AngularNodeAppEngine({
  // Trust all X-Forwarded-* headers
  trustProxyHeaders: true, 
});
```

#### Patches

-   22.0.0-next.7
-   21.2.9
-   20.3.25
-   19.2.25

#### Resources

-   [https://github.com/angular/angular-cli/pull/33031](https://github.com/angular/angular-cli/pull/33031)
-   [https://angular.dev/best-practices/security#configuring-trusted-proxy-headers](https://angular.dev/best-practices/security#configuring-trusted-proxy-headers)

## Affected Packages

4 total 4 fixed

Ecosystem

Package

Vulnerable range

Fix

📦npm

`@angular/ssr` 

≥ 22.0.0-next.0&&< 22.0.0-next.7

22.0.0-next.7`npm install @angular/ssr@22.0.0-next.7`

📦npm

`@angular/ssr` 

≥ 21.0.0-next.0&&< 21.2.9

21.2.9`npm install @angular/ssr@21.2.9`

📦npm

`@angular/ssr` 

≥ 20.0.0-next.0&&< 20.3.25

20.3.25`npm install @angular/ssr@20.3.25`

📦npm

`@angular/ssr` 

≥ 19.0.0-next.0&&< 19.2.25

19.2.25`npm install @angular/ssr@19.2.25`

## Affected Products

1 product · 10 configurations

Application

`angular cli`angular

≥ 21.0.0 && < 21.2.9

1 version

22.0.0

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @angular/ssr, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update @angular/ssr to 22.0.0-next.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44437 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.
    

## Frequently Asked Questions

\### Description A vulnerability exists in the \`X-Forwarded-Prefix\` header processing logic within Angular SSR. The internal validation mechanism fails to properly account for URL-encoded characters, specifically dots (\`%2e%2e\`). This allows an attacker to bypass security filters by injecting encoded path traversal sequences that are later decoded and utilized by the application logic. When an Angular SSR application is configured to trust proxy headers and is deployed behind a proxy that forwards the \`X-Forwarded-Prefix\` header without prior sanitization, an attacker can provide a payload such

O3 Security · Impact-Aware SCA

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