CVE-2026-45133: symfony — Fix

Description

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 worker. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12.

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CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0069

Probability of exploitation

0.49%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-674 CWE-674

CWE-776 CWE-776

CWE-1333 CWE-1333

Affected Products

Vendor	Product	Versions
sensiolabs	symfony	< 5.4.52
sensiolabs	symfony	6.0.0 — 6.4.40
sensiolabs	symfony	7.0.0 — 7.4.12
sensiolabs	symfony	8.0.0 — 8.0.12

References

Advisories & Patches

https://github.com/symfony/symfony/security/advisories/GHSA-c2p3-7m5p-cv8x

Other References

https://github.com/symfony/symfony/releases/tag/v5.4.52 https://github.com/symfony/symfony/releases/tag/v6.4.40 https://github.com/symfony/symfony/releases/tag/v7.4.12 https://github.com/symfony/symfony/releases/tag/v8.0.12

Frequently Asked Questions

What is CVE-2026-45133? +

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 worker. This issue is fixed in versions 5.4.52, 6.4.40, 7.4.12, and 8.0.12. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-45133? +

CVE-2026-45133 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0069, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-45133? +

CVE-2026-45133 affects products from sensiolabs, specifically: symfony. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-45133? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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