Summary
symfony/ux-autocomplete: XSS via unescaped AJAX response data
Description
The Stimulus controller shipped with symfony/ux-autocomplete renders AJAX response items into the dropdown by interpolating the text field directly into HTML template literals (<div>${item[labelField]}</div>) inside _createAutocompleteWithRemoteData(). The value is parsed as HTML rather than text, so any markup contained in the AJAX response is executed by the browser.
When the dropdown values are derived from user-supplied content, an attacker can craft a string that triggers stored XSS in the browser of any other user who later opens a page containing an autocomplete widget backed by the same data.
Resolution
The option and item renderers used in _createAutocompleteWithRemoteData() now use TomSelect's escape helper to HTML-escape the value by default. Endpoints that legitimately return HTML (for example, to highlight the search term) can opt back in to the previous behavior by setting options_as_html: true. The AutocompleteChoiceTypeExtension normalizer that previously forced options_as_html=false when autocomplete_url was set has been dropped so the opt-in is reachable from the form layer.
The patch for this issue is available here for branch 2.x (and forward-ported to 3.x).
Credits
Symfony would like to thank Alex Ashkov for reporting the issue and Hugo Alliaume for providing the fix.
Impact
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.
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symfony/ux-autocomplete to 2.36.0 or later; symfony/ux-autocomplete to 3.1.0 or later
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Frequently Asked Questions
- What is CVE-2026-49216? CVE-2026-49216 is a medium-severity cross-site scripting (XSS) vulnerability in symfony/ux-autocomplete (composer), affecting versions >= 2.2.0, < 2.36.0. It is fixed in 2.36.0, 3.1.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of symfony/ux-autocomplete are affected by CVE-2026-49216? symfony/ux-autocomplete (composer) versions >= 2.2.0, < 2.36.0 is affected.
- Is there a fix for CVE-2026-49216? Yes. CVE-2026-49216 is fixed in 2.36.0, 3.1.0. Upgrade to this version or later.
- Is CVE-2026-49216 exploitable, and should I be worried? Whether CVE-2026-49216 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-2026-49216 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-2026-49216?
- Upgrade
symfony/ux-autocompleteto 2.36.0 or later - Upgrade
symfony/ux-autocompleteto 3.1.0 or later
- Upgrade