CVE-2026-55877 is a medium-severity cross-site scripting (XSS) vulnerability in symfony/ux-icons (composer), affecting versions >= 2.17.0, < 2.36.1. It is fixed in 2.36.1, 3.2.0.
Description The uxicon() Twig function is marked issafe=['html'], so Twig never escapes its output. Icon::toHtml() inlines the SVG source verbatim into the page. Browsers execute <script> elements and on event-handler attributes found inside inline SVG, making any unsanitized icon a vector for cross-site scripting. Two code paths were affected. In the local file path, Icon::fromFile() only stripped <script> elements that were direct children of <svg>, leaving nested scripts and all on attributes untouched despite a code comment claiming broader protection. In the Iconify on-demand path (enabled by default), the remote JSON body field was wrapped into an Icon object with no sanitization at all. Concrete attack vectors include a malicious SVG icon pack from a third-party theme or downloaded icon set, or a controlled Iconify endpoint configured via iconify.endpoint (including a poisoned cache). Resolution Introducing an IconFactory that centralizes sanitization across every icon source before an Icon object is created. The sanitizer removes script-capable elements (script, foreignObject, iframe, object, embed), SMIL animations targeting on, href, or xlink:href attributes, CDATA sections, processing instructions, all on attributes, and javascript:, vbscript:, and data:text/html URL schemes. <style> elements are kept for theming but have any handlers stripped. Icons that contain none of these constructs are byte-for-byte identical after sanitization. Credits Symfony would like to thank Pascal Cescon for reporting the issue and Hugo Alliaume for providing the fix.
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-2026-55877 has a CVSS score of 6.1 (Medium). 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 (2.36.1, 3.2.0). Upgrading removes the vulnerable code path.
composer
symfony/ux-icons (>= 2.17.0, < 2.36.1)symfony/ux-icons (>= 3.0.0, < 3.2.0)symfony/ux-icons → 2.36.1 (composer)symfony/ux-icons → 3.2.0 (composer)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 instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-55877 is reachable in your applications. Explore open-source security for your team.
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Upgrade the following packages to resolve this vulnerability:
symfony/ux-icons to 2.36.1 or latersymfony/ux-icons to 3.2.0 or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-55877 is a medium-severity cross-site scripting (XSS) vulnerability in symfony/ux-icons (composer), affecting versions >= 2.17.0, < 2.36.1. It is fixed in 2.36.1, 3.2.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
CVE-2026-55877 has a CVSS score of 6.1 (Medium). 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.
symfony/ux-icons (composer) versions >= 2.17.0, < 2.36.1 is affected.
Yes. CVE-2026-55877 is fixed in 2.36.1, 3.2.0. Upgrade to this version or later.
Whether CVE-2026-55877 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
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.
symfony/ux-icons to 2.36.1 or latersymfony/ux-icons to 3.2.0 or later