CVE-2026-55877 Symfony UX: XSS in symfony/ux-icons via unsanitized SVG content in local files and Iconify on-demand responses
Attackers can execute cross-site scripting via unsanitized SVG content in Symfony UX Icons, requiring an upgrade to patched versions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-55877?
CVE-2026-55877 is a medium-severity cross-site scripting vulnerability in symfony ux, published on 8 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Symfony UX is a JavaScript ecosystem for Symfony. From 2.17.0 before 2.36.1 and from 3.0.0 before 3.2.0, the ux_icon() Twig function is marked is_safe=['html'] and Icon::toHtml() inlines SVG source verbatim, allowing unsanitized local SVG files or Iconify on-demand JSON body responses containing nested script elements, on* event handlers, or dangerous URL schemes to execute cross-site scripting. This issue is fixed in versions 2.36.1 and 3.2.0.
Weakness: CWE-79
Which versions are affected by CVE-2026-55877?
4 open source packages ship an affected version, including symfony/ux-icons. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
symfony/ux-icons Packagist | From 2.17.0 | 2.36.1 |
symfony/ux-icons Packagist | From 2.17.0 | 2.36.1 |
symfony/ux-icons Packagist | From 3.0.0 | 3.2.0 |
symfony/ux-icons Packagist | From 3.0.0 | 3.2.0 |
Products include Symfony Ux.
How do I fix CVE-2026-55877?
Upgrade symfony/ux-icons to a fixed version for your release line: 2.36.1 or 3.2.0.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55877 being exploited?
There is no known exploitation of CVE-2026-55877 in the wild and no public exploit code.
Other vulnerabilities in symfony ux
- CVE-2026-49208 Symfony UX: Format-less date LiveProps parsed with the permissive DateTime constructor
- CVE-2026-49211 Symfony UX: Information exposure via unescaped LIKE wildcards in EntitySearchUtil
- CVE-2026-49212 Symfony UX: LiveComponentHydrator HMAC checksum lacks component and slot binding
- CVE-2026-49209 Symfony UX: Denial of service in symfony/ux-live-component via unbounded batch action requests
- CVE-2026-49216 Symfony UX: XSS in symfony/ux-autocomplete via unescaped AJAX response data
Sources
Also known as GHSA-6v8j-33hc-mv84.