CVE-2026-50555

A Cross-Site Scripting (XSS) vulnerability exists in @angular/platform-server's DOM emulation dependency (domino) when serializing the content of raw-text elements (such as <script>, <style>, and <iframe>).

domino supports escaping raw-text elements during serialization to prevent closing-tag breakout. However, a Unicode index alignment bug existed in this escaping logic.

In JavaScript, string lengths and character indices are calculated based on UTF-16 code units (where astral characters, such as emojis, occupy 2 code units / 4 bytes). If the bound dynamic text contained astral Unicode characters before the closing tag (e.g. </script>, </style>, or </iframe>), the index offset calculation in domino's replacement logic shifted.

This misalignment caused domino to fail to replace or escape the closing tag, leaving it raw and unescaped in the output HTML.

An attacker who controls the dynamic text can supply a payload containing both an astral Unicode character and a closing tag (e.g., 😀</iframe><script>alert(1)</script>). When serialized on the server during SSR, the browser parses the unescaped closing tag, exits the raw-text context early, and executes the subsequent <script> block, leading to same-origin Cross-Site Scripting (XSS).

Patched Versions

• 22.0.0-rc.2
• 21.2.16
• 20.3.24
• 19.2.25

Workarounds

If you cannot immediately update your dependencies, you can:

• Avoid binding user-controlled values inside <iframe> or other raw-text elements.
• Sanitize any user input placed inside raw-text elements to explicitly strip closing tags before passing it to the template.

This vulnerability allows an attacker to perform same-origin Cross-Site Scripting (XSS) attacks against any user visiting an SSR-rendered page that binds user-controlled data inside raw-text elements. This can lead to session hijacking, credentials theft, unauthorized actions on behalf of users, and defacement.

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

1. What is CVE-2026-50555? CVE-2026-50555 is a high-severity cross-site scripting (XSS) vulnerability in @angular/platform-server (npm), affecting versions >= 22.0.0-next.0, < 22.0.0-rc.2. It is fixed in 22.0.0-rc.2, 21.2.16, 20.3.24, 19.2.25. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. Which versions of @angular/platform-server are affected by CVE-2026-50555? @angular/platform-server (npm) versions >= 22.0.0-next.0, < 22.0.0-rc.2 is affected.
3. Is there a fix for CVE-2026-50555? Yes. CVE-2026-50555 is fixed in 22.0.0-rc.2, 21.2.16, 20.3.24, 19.2.25. Upgrade to this version or later.
4. Is CVE-2026-50555 exploitable, and should I be worried? Whether CVE-2026-50555 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-2026-50555 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-2026-50555?
   • Upgrade @angular/platform-server to 22.0.0-rc.2 or later
   • Upgrade @angular/platform-server to 21.2.16 or later
   • Upgrade @angular/platform-server to 20.3.24 or later
   • Upgrade @angular/platform-server to 19.2.25 or later