Summary
Description
A Cross-site Scripting (CWE-79) vulnerability in Qwik.js' server-side rendering virtual attribute serialization allows a remote attacker to inject arbitrary web scripts into server-rendered pages via virtual attributes. Successful exploitation permits script execution in a victim's browser in the context of the affected origin. This affects qwik-city before version 1.19.0. This has been patched in qwik-city version 1.19.0.
Impact
This vulnerability impacts applications that dynamically populate Virtual Node attributes with keys/values that users can influence. Applications that hard-code these keys/values are unaffected.
Qwik doesn't use traditional hydration. Instead, it serializes application state into the HTML so the client can resume execution from the server-rendered output. To support this, Qwik v1 marks component boundaries with HTML comments. SSR builds comment content for Virtual components by concatenating structural attribute names and values without any escaping or quoting. An attacker-controlled key or value can prematurely close the HTML comment and inject arbitrary HTML/JS.
Successful exploitation permits script execution in a victim’s browser in the context of the affected origin. Additionally, because Qwik uses these serialized comment markers for resumability, breaking comment structure can lead to resume/hydration desync and unexpected client-side behavior.
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.
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.
Remediation advice
This has been patched in qwik-city version 1.19.0. Users are strongly encouraged to update to the latest available release.
Frequently Asked Questions
- What is CVE-2026-25148? CVE-2026-25148 is a medium-severity cross-site scripting (XSS) vulnerability in @builder.io/qwik-city (npm), affecting versions < 1.19.0. It is fixed in 1.19.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of @builder.io/qwik-city are affected by CVE-2026-25148? @builder.io/qwik-city (npm) versions < 1.19.0 is affected.
- Is there a fix for CVE-2026-25148? Yes. CVE-2026-25148 is fixed in 1.19.0. Upgrade to this version or later.
- Is CVE-2026-25148 exploitable, and should I be worried? Whether CVE-2026-25148 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-2026-25148 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-2026-25148? Upgrade
@builder.io/qwik-cityto 1.19.0 or later.