Summary
@angular/platform-server: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
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.
Impact
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.
CVE-2026-50555 has a CVSS score of 6.1 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (22.0.0-rc.2, 21.2.16, 20.3.24, 19.2.25); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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@angular/platform-server to 22.0.0-rc.2 or later; @angular/platform-server to 21.2.16 or later; @angular/platform-server to 20.3.24 or later; @angular/platform-server to 19.2.25 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- 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.
- How severe is CVE-2026-50555? CVE-2026-50555 has a CVSS score of 6.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- 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.
- 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.
- 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
- 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.
- How do I fix CVE-2026-50555?
- Upgrade
@angular/platform-serverto 22.0.0-rc.2 or later - Upgrade
@angular/platform-serverto 21.2.16 or later - Upgrade
@angular/platform-serverto 20.3.24 or later - Upgrade
@angular/platform-serverto 19.2.25 or later
- Upgrade