CVE-2026-31822

Workarounds

Override the vulnerable JavaScript controller at the project level.

Note: Step 2 differs between Sylius 2.0 and up

Step 1. Override JavaScript controller handling login

Patch ApiLoginController.js

Copy the original from vendor/sylius/sylius/src/Sylius/Bundle/ShopBundle/Resources/assets/controllers/ApiLoginController.js to assets/shop/controllers/ApiLoginController.js and apply:

...
  .then(response => {
    if (response.success) {
      window.location.reload();
    } else {
      const errorElement = this.errorPrototypeTarget.cloneNode(true);
-     errorElement.innerHtml = response.message;
+     errorElement.textContent = response.message;
      this.errorTarget.innerHTML = errorElement.outerHTML;
    }
  })
...

Step 2. Register the patched controller

Sylius 2.1+ (Stimulus Bridge with controllers.json)

Disable the vendor controller in assets/shop/controllers.json:

...
  "api-login": {
-    "enabled": true,
+    "enabled": false,
    "fetch": "lazy"
  }
...

Register the overwritten controller in assets/shop/bootstrap.js

import ApiLoginController from './controllers/ApiLoginController'

app.register('sylius--shop-bundle--api-login', ApiLoginController);

Sylius 2.0 (explicit imports in vendor app.js)

Use Webpack's NormalModuleReplacementPlugin to swap the controller at build time. In webpack.config.js, after shopConfig is created:

+ const webpack = require('webpack');
...
  // Shop config
  const shopConfig = SyliusShop.getWebpackConfig(path.resolve(__dirname));
+ shopConfig.plugins.push(
+   new webpack.NormalModuleReplacementPlugin(
+     /\/controllers\/ApiLoginController\.js$/,
+     path.resolve(__dirname, 'assets/shop/controllers/ApiLoginController.js')
+   )
+ );
...

Step 3. Rebuild assets

yarn encore dev  # or: yarn encore production

Reporters

We would like to extend our gratitude to the following individuals for their detailed reporting and responsible disclosure of this vulnerability:

• Bartłomiej Nowiński (@bnBart)

For more information

If you have any questions or comments about this advisory:

• Open an issue in Sylius issues
• Email us at [email protected]

A cross-site scripting (XSS) vulnerability exists in the shop checkout login form handled by the ApiLoginController Stimulus controller.

When a login attempt fails, AuthenticationFailureHandler returns a JSON response whose message field is rendered into the DOM using innerHTML, allowing any HTML or JavaScript in that value to be parsed and executed by the browser.

The message value originates from AuthenticationException::getMessageKey() passed through Symfony's translator (security domain, using the request locale). In the default Sylius installation, this returns a hardcoded translation key (e.g. "Invalid credentials."), which is not directly user-controlled. However, using innerHTML with server-derived data violates defense-in-depth principles, and the risk escalates significantly under realistic scenarios:

• Customized authentication handlers, if a project overrides AuthenticationFailureHandler to include user-supplied data in the message (e.g. "No account found for "), an attacker can inject arbitrary JavaScript directly via the login
  form without any privileged access.
• Translation injection, if translation files are sourced from an untrusted database or CMS and contain HTML, the message could carry a malicious payload.
• Man-in-the-Middle, if the response is intercepted (e.g. on HTTP or via a compromised proxy), an attacker can inject arbitrary HTML/JS into the message field.
• Server-side injection, if any middleware, reverse proxy, or error handler modifies the JSON response body, malicious content could be injected into the message field.

Exploitation could lead to session hijacking, credential theft, cart/order manipulation, or phishing within the trusted shop domain.

The vulnerability affects all Sylius installations that use the default shop checkout login form with the bundled ApiLoginController.js.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

Kodem intelligence

The issue is fixed in versions: 2.0.16, 2.1.12, 2.2.3 and above.

1. What is CVE-2026-31822? CVE-2026-31822 is a medium-severity cross-site scripting (XSS) vulnerability in sylius/sylius (composer), affecting versions >= 2.0.0, <= 2.0.15. It is fixed in 2.0.16, 2.1.12, 2.2.3. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. Which versions of sylius/sylius are affected by CVE-2026-31822? sylius/sylius (composer) versions >= 2.0.0, <= 2.0.15 is affected.
3. Is there a fix for CVE-2026-31822? Yes. CVE-2026-31822 is fixed in 2.0.16, 2.1.12, 2.2.3. Upgrade to this version or later.
4. Is CVE-2026-31822 exploitable, and should I be worried? Whether CVE-2026-31822 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2026-31822 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2026-31822?
   • Upgrade sylius/sylius to 2.0.16 or later
   • Upgrade sylius/sylius to 2.1.12 or later
   • Upgrade sylius/sylius to 2.2.3 or later