{"id":"CVE-2026-49210","aliases":["EUVD-2026-45210","GHSA-38x5-rcv4-xf7x"],"status":"published","title":"Symfony UX: XSS in symfony/ux-live-component via attacker-controlled child component tag","description":"Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, Symfony\\UX\\LiveComponent\\Util\\ChildComponentPartialRenderer::createHtml() interpolates the client-controlled children[id].tag value from LiveComponentSubscriber and InterceptChildComponentRenderSubscriber directly into HTML as a tag name without escaping or validation, allowing arbitrary HTML, including \u003cscript\u003e tags, on any Live Component re-render that contains at least one child component. This issue is fixed in versions 2.36.0 and 3.1.0.","severity":{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00338,"percentile":0.27397,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-79"],"published":"2026-06-19T19:34:49Z","modified":"2026-10-28T02:30:29Z","fixes":[{"ecosystem":"Packagist","package":"symfony/ux-live-component","fixed_in":["2.36.0","3.1.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Packagist","package":"symfony/ux-live-component","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.8.0"},{"fixed":"2.36.0"}]}]},{"source":"ghsa","ecosystem":"Packagist","package":"symfony/ux-live-component","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.0"},{"fixed":"3.1.0"}]}]},{"source":"osv","ecosystem":"Packagist","package":"symfony/ux-live-component","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.8.0"},{"fixed":"2.36.0"}]}],"versions":["v2.10.0","v2.11.0","v2.11.1","v2.11.2","v2.12.0","v2.13.0","v2.13.1","v2.13.2","v2.13.3","v2.14.0","v2.14.1","v2.14.2","v2.15.0","v2.16.0","v2.17.0","v2.18.0","v2.18.1","v2.19.0","v2.19.2","v2.20.0","v2.21.0","v2.22.0","v2.22.1","v2.23.0","v2.24.0","v2.25.0","v2.25.1","v2.25.2","v2.26.0","v2.26.1","v2.27.0","v2.28.0","v2.28.1","v2.28.2","v2.29.0","v2.29.1","v2.29.2","v2.30.0","v2.31.0","v2.32.0","v2.33.0","v2.34.0","v2.35.0","v2.8.0","v2.8.1","v2.9.0","v2.9.1"]},{"source":"osv","ecosystem":"Packagist","package":"symfony/ux-live-component","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.0.0"},{"fixed":"3.1.0"}]}],"versions":["v3.0.0"]}],"products":[{"vendor":"symfony","product":"ux"}],"references":[{"url":"https://github.com/symfony/ux/security/advisories/GHSA-38x5-rcv4-xf7x","tags":["x_refsource_CONFIRM","Vendor Advisory","advisory","web"]},{"url":"https://github.com/symfony/ux/commit/fbc5e9a1bda7e4556be21bb1d970f382760ed9a9","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/symfony/ux/releases/tag/v2.36.0","tags":["x_refsource_MISC","Release Notes","web"]},{"url":"https://github.com/symfony/ux/releases/tag/v3.1.0","tags":["x_refsource_MISC","Release Notes","web"]},{"url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/ux-live-component/CVE-2026-49210.yaml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-38x5-rcv4-xf7x"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49210.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49210","tags":["advisory"]},{"url":"https://github.com/symfony/ux","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-49210","title":"Symfony UX: XSS in symfony/ux-live-component via attacker-controlled child component tag","description":"Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, Symfony\\UX\\LiveComponent\\Util\\ChildComponentPartialRenderer::createHtml() interpolates the client-controlled children[id].tag value from LiveComponentSubscriber and InterceptChildComponentRenderSubscriber directly into HTML as a tag name without escaping or validation, allowing arbitrary HTML, including \u003cscript\u003e tags, on any Live Component re-render that contains at least one child component. This issue is fixed in versions 2.36.0 and 3.1.0.","status":"published","published":"2026-07-17T16:09:17.85Z","modified":"2026-07-17T16:52:59.836Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low","assessor":"cna"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T13:35:10.963527Z"}],"euvd":[{"id":"EUVD-2026-45210","description":"Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, Symfony\\UX\\LiveComponent\\Util\\ChildComponentPartialRenderer::createHtml() interpolates the client-controlled children[id].tag value from LiveComponentSubscriber and InterceptChildComponentRenderSubscriber directly into HTML as a tag name without escaping or validation, allowing arbitrary HTML, including \u003cscript\u003e tags, on any Live Component re-render that contains at least one child component. This issue is fixed in versions 2.36.0 and 3.1.0.","status":"published","published":"2026-07-17T16:09:17Z","modified":"2026-07-17T16:52:59Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low"}],"updated_at":"2026-11-02T18:19:50.451546Z"}],"ghsa":[{"id":"GHSA-38x5-rcv4-xf7x","title":"symfony/ux-live-component: XSS via attacker-controlled child component tag","description":"### Description\n\n`Symfony\\UX\\LiveComponent\\Util\\ChildComponentPartialRenderer::createHtml()` interpolates the `$childTag` argument directly into the HTML output as a tag name, without escaping or validation. The value originates from client-controlled JSON (`children[id].tag`) parsed by `LiveComponentSubscriber` and propagated through `InterceptChildComponentRenderSubscriber`, so an attacker who can reach the Live Component endpoint can inject arbitrary HTML, including `\u003cscript\u003e` tags, on any re-render of a Live Component that contains at least one child component.\n\nIn the default configuration, the Live Component endpoint is gated by an `Accept: application/vnd.live-component+html` request-header check that cannot be set cross-origin without a CORS preflight, so the issue is primarily a defense-in-depth gap. It becomes directly exploitable on applications that have relaxed CORS to allow this header from untrusted origins, or that have been pivoted from another same-origin XSS.\n\n### Resolution\n\n`ChildComponentPartialRenderer` now validates `$childTag` against a strict HTML tag-name regex before interpolating it, and rejects any value that doesn't match. Anything that wouldn't be a valid HTML tag is dropped before reaching the response.\n\nThe patch for this issue is available [here](https://github.com/symfony/ux/commit/fbc5e9a1bda7e4556be21bb1d970f382760ed9a9) for branch 2.x (and forward-ported to 3.x).\n\n### Credits\n\nSymfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.","status":"published","published":"2026-06-19T19:34:49Z","modified":"2026-06-19T19:34:51Z","cvss":[{"version":"4.0","score":5.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"medium"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:40:30.53004Z"}],"nvd":[{"id":"CVE-2026-49210","description":"Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, Symfony\\UX\\LiveComponent\\Util\\ChildComponentPartialRenderer::createHtml() interpolates the client-controlled children[id].tag value from LiveComponentSubscriber and InterceptChildComponentRenderSubscriber directly into HTML as a tag name without escaping or validation, allowing arbitrary HTML, including \u003cscript\u003e tags, on any Live Component re-render that contains at least one child component. This issue is fixed in versions 2.36.0 and 3.1.0.","status":"published","published":"2026-07-17T17:17:15.65Z","modified":"2026-10-24T20:10:00.137Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"low","assessor":"secondary"},{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:12:30.250437Z"}],"osv":[{"id":"CVE-2026-49210","title":"Symfony UX: XSS in symfony/ux-live-component via attacker-controlled child component tag","description":"Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, Symfony\\UX\\LiveComponent\\Util\\ChildComponentPartialRenderer::createHtml() interpolates the client-controlled children[id].tag value from LiveComponentSubscriber and InterceptChildComponentRenderSubscriber directly into HTML as a tag name without escaping or validation, allowing arbitrary HTML, including \u003cscript\u003e tags, on any Live Component re-render that contains at least one child component. This issue is fixed in versions 2.36.0 and 3.1.0.","status":"published","published":"2026-07-17T16:09:17.85Z","modified":"2026-10-28T02:30:29.540489036Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:45:07.060148Z"},{"id":"GHSA-38x5-rcv4-xf7x","title":"symfony/ux-live-component: XSS via attacker-controlled child component tag","description":"### Description\n\n`Symfony\\UX\\LiveComponent\\Util\\ChildComponentPartialRenderer::createHtml()` interpolates the `$childTag` argument directly into the HTML output as a tag name, without escaping or validation. The value originates from client-controlled JSON (`children[id].tag`) parsed by `LiveComponentSubscriber` and propagated through `InterceptChildComponentRenderSubscriber`, so an attacker who can reach the Live Component endpoint can inject arbitrary HTML, including `\u003cscript\u003e` tags, on any re-render of a Live Component that contains at least one child component.\n\nIn the default configuration, the Live Component endpoint is gated by an `Accept: application/vnd.live-component+html` request-header check that cannot be set cross-origin without a CORS preflight, so the issue is primarily a defense-in-depth gap. It becomes directly exploitable on applications that have relaxed CORS to allow this header from untrusted origins, or that have been pivoted from another same-origin XSS.\n\n### Resolution\n\n`ChildComponentPartialRenderer` now validates `$childTag` against a strict HTML tag-name regex before interpolating it, and rejects any value that doesn't match. Anything that wouldn't be a valid HTML tag is dropped before reaching the response.\n\nThe patch for this issue is available [here](https://github.com/symfony/ux/commit/fbc5e9a1bda7e4556be21bb1d970f382760ed9a9) for branch 2.x (and forward-ported to 3.x).\n\n### Credits\n\nSymfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.","status":"published","published":"2026-06-19T19:34:49Z","modified":"2026-09-10T03:51:07.753980491Z","cvss":[{"version":"4.0","score":5.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"medium"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:46:35.406455Z"}]}}