CVE-2026-45133: Symfony is a PHP framework for web and console applications and a set of reusable PHP components

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HIGH 7.5REMOTEUPGRADE

CVE-2026-45133 is a high-severity flaw (CVSS 7.5) affecting symfony. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, when the parser is exposed to attacker-controlled input, deeply nested mappings or sequences cause both the block-level (Parser::parseBlock()) and inline (Inline::parseSequence() / Inline::parseMapping()) parsers to recurse without a depth limit. A crafted document exhausts the PHP stack and crashes the wo

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	0.6% (top 50%)
CISA exploited list	No
Weakness	CWE-674, CWE-776, CWE-1333
Published	2026-07-14
Last modified	2026-07-15

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

Last updated 2026-07-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-14 19:17 UTCPublished CVE record published
2026-07-15 14:54 UTCUpdated Record last modified

sensiolabs symfony UPGRADE

Affected: < 5.4.52 · >= 6.0.0 and < 6.4.40 · >= 7.0.0 and < 7.4.12 · >= 8.0.0 and < 8.0.12

Fixed in: 5.4.52, 6.4.40, 7.4.12, 8.0.12

Safe to downgrade to: a release before 6.0.0

1. Check installed version

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

2. UPGRADE to 5.4.52 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade symfony

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 6.0.0 (Debian / Ubuntu)

apt-cache madison symfony sudo apt install symfony=<VERSION_BEFORE_6.0.0> sudo apt-mark hold symfony

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

dnf --showduplicates list symfony sudo dnf downgrade symfony-<VERSION_BEFORE_6.0.0> sudo dnf versionlock add symfony

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-2026-45133?

symfony: upgrade to 5.4.52, 6.4.40, 7.4.12, 8.0.12. Exact commands for each OS are on this page.

Is CVE-2026-45133 being exploited?

CVE-2026-45133 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-2026-45133 affect?

CVE-2026-45133 affects symfony. Severity is high (CVSS 7.5). Symfony is a PHP framework for web and console applications and a set of reusable PHP components. Prior to 5.4.52, 6.4.40, 7.4.12, and 8.0.12, when the parser is exposed to attacker-controlled input, deeply nested mappings or sequences caus

How urgent is CVE-2026-45133?

Priority 44/100. High severity; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

Related CVEs

CVE-2026-45073 HIGH 7.3 UPGRADE Symfony is a PHP framework for web and console applications and a set of reusable PHP components
CVE-2026-45064 MEDIUM 6.1 UPGRADE Symfony is a PHP framework for web and console applications and a set of reusable PHP components
CVE-2026-48761 MEDIUM 6.1 UPGRADE Symfony is a PHP framework for web and console applications and a set of reusable PHP components
CVE-2026-45756 HIGH 7.5 UPGRADE Symfony is a PHP framework for web and console applications and a set of reusable PHP components
CVE-2026-45754 MEDIUM 5.3 UPGRADE Symfony is a PHP framework for web and console applications and a set of reusable PHP components

References

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