CVE-2026-49212: Symfony UX is a JavaScript ecosystem for Symfony

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-49212 is a high-severity flaw (CVSS 7.5) 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 2.8.0 until 2.36.0 and 3.1.0, the HMAC computed by Symfony\UX\LiveComponent\LiveComponentHydrator covered only sorted prop key/value pairs and did not include the component name, the slot identifier (props vs propsFromParent), or request context, allowing a signed blob minted for one component or slot to be replayed in another and set a read-only prop on a target component. This issue is fixe

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-345
Published	2026-07-17
Last modified	2026-10-24

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

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-17 17:17 UTCPublished CVE record published
2026-10-24 20:10 UTCUpdated Record last modified

symfony ux UPGRADE

Affected: >= 2.8.0 and < 2.36.0 · 3.0.0

Fixed in: 2.36.0

Safe to downgrade to: a release before 2.8.0

1. Check installed version

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

2. UPGRADE to 2.36.0 (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 2.8.0 (Debian / Ubuntu)

apt-cache madison ux sudo apt install ux=<VERSION_BEFORE_2.8.0> 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_2.8.0> 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-2026-49212?

ux: upgrade to 2.36.0. Exact commands for each OS are on this page.

Is CVE-2026-49212 being exploited?

CVE-2026-49212 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-2026-49212 affect?

CVE-2026-49212 affects ux. Severity is high (CVSS 7.5). Symfony UX is a JavaScript ecosystem for Symfony. From 2.8.0 until 2.36.0 and 3.1.0, the HMAC computed by Symfony\UX\LiveComponent\LiveComponentHydrator covered only sorted prop key/value pairs and did not include the component name, the sl

How urgent is CVE-2026-49212?

Priority 35/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-49211 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
CVE-2026-49216 MEDIUM 5.4 UPGRADE Symfony UX is a JavaScript ecosystem for Symfony

References

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