CVE-2026-55877: Symfony UX is a JavaScript ecosystem for Symfony

Routine

MEDIUM 6.1UPGRADE

CVE-2026-55877 is a medium-severity flaw (CVSS 6.1) affecting ux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-07-08
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: symfony

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-08 22:17 UTCPublished CVE record published
2026-10-25 17:10 UTCUpdated Record last modified

symfony ux UPGRADE

Affected: >= 2.17.0 and < 2.36.1 · >= 3.0.0 and < 3.2.0

Fixed in: 2.36.1, 3.2.0

Safe to downgrade to: a release before 2.17.0

1. Check installed version

apt-cache policy ux || rpm -q ux || ux --version

2. UPGRADE to 2.36.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade ux

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ux

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.17.0 (Debian / Ubuntu)

apt-cache madison ux sudo apt install ux=<VERSION_BEFORE_2.17.0> sudo apt-mark hold ux

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list ux sudo dnf downgrade ux-<VERSION_BEFORE_2.17.0> sudo dnf versionlock add ux

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-55877?

ux: upgrade to 2.36.1, 3.2.0. Exact commands for each OS are on this page.

Is CVE-2026-55877 being exploited?

CVE-2026-55877 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-55877 affect?

CVE-2026-55877 affects ux. Severity is medium (CVSS 6.1). 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 f

How urgent is CVE-2026-55877?

Priority 28/100. No elevated risk signals yet.

Related CVEs

CVE-2026-49211 HIGH 7.5 UPGRADE Symfony UX is a JavaScript ecosystem for Symfony
CVE-2026-49212 HIGH 7.5 UPGRADE Symfony UX is a JavaScript ecosystem for Symfony
CVE-2026-49209 MEDIUM 6.5 UPGRADE Symfony UX is a JavaScript ecosystem for Symfony
CVE-2026-49208 MEDIUM 5.3 UPGRADE Symfony UX is a JavaScript ecosystem for Symfony
CVE-2026-49210 MEDIUM 6.1 UPGRADE Symfony UX is a JavaScript ecosystem for Symfony

References

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