CVE-2026-49209: Symfony UX is a JavaScript ecosystem for Symfony

Routine

MEDIUM 6.5UPGRADE

CVE-2026-49209 is a medium-severity flaw (CVSS 6.5) 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 2.5.0 until 2.36.0 and 3.1.0, Symfony\UX\LiveComponent\Controller\BatchActionController::__invoke() iterates over the client-supplied actions array and issues a full HttpKernel sub-request for each entry; because the array size is never bounded, an authenticated client can submit a single _batch request containing thousands of actions and exhaust CPU, memory, and database connections on the a

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.6% (top 54%)
CISA exploited list	No
Weakness	CWE-770
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: >= 2.5.0 and < 2.36.0 · 3.0.0

Fixed in: 2.36.0

Safe to downgrade to: a release before 2.5.0

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 2.5.0 (Debian / Ubuntu)

apt-cache madison ux sudo apt install ux=<VERSION_BEFORE_2.5.0> 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_2.5.0> 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-2026-49209?

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

Is CVE-2026-49209 being exploited?

CVE-2026-49209 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-2026-49209 affect?

CVE-2026-49209 affects ux. Severity is medium (CVSS 6.5). Symfony UX is a JavaScript ecosystem for Symfony. From 2.5.0 until 2.36.0 and 3.1.0, Symfony\UX\LiveComponent\Controller\BatchActionController::__invoke() iterates over the client-supplied actions array and issues a full HttpKernel sub-requ

How urgent is CVE-2026-49209?

Priority 34/100. 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-2026-49208 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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