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CVE-2026-45133

Symfony: [Yaml] Harden the parser when handling untrusted input

HIGH
7.5
CVSS Score
Published: July 14, 2026 at 06:45 PM UTC
Updated: July 15, 2026 at 03:14 PM UTC
2 products affected across 2 vendorsSymfonySymfony

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Severity
HIGH7.5
Exploit prediction
EPSS 0.6%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Symfony· Sensiolabsdrupal
95%
v < 5.4.526.0.0 ≤ v < 6.4.407.0.0 ≤ v < 7.4.128.0.0 ≤ v < 8.0.12
Affected range stops below 5.4.52, so it looks safe — our inference, not a vendor statement
Affected range stops below 6.4.40, so it looks safe — our inference, not a vendor statement
Affected range stops below 7.4.12, so it looks safe — our inference, not a vendor statement
Affected range stops below 8.0.12, so it looks safe — our inference, not a vendor statement
Symfony· Symfonycomposer
60%
v < 5.4.52v < 6.4.40v < 7.4.12v < 8.0.12
Affected range stops below 5.4.52, so it looks safe — our inference, not a vendor statement
Affected range stops below 6.4.40, so it looks safe — our inference, not a vendor statement
Affected range stops below 7.4.12, so it looks safe — our inference, not a vendor statement
Affected range stops below 8.0.12, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

x_refsource_CONFIRMPatchVendor Advisory
Source: cverecord
https://github.com/symfony/symfony/security/advisories/GHSA-c2p3-7m5p-cv8x
x_refsource_MISCProductRelease Notes
Source: cverecord
https://github.com/symfony/symfony/releases/tag/v5.4.52
x_refsource_MISCProductRelease Notes
Source: cverecord
https://github.com/symfony/symfony/releases/tag/v6.4.40
x_refsource_MISCProductRelease Notes
Source: cverecord
https://github.com/symfony/symfony/releases/tag/v7.4.12
x_refsource_MISCProductRelease Notes
Source: cverecord
https://github.com/symfony/symfony/releases/tag/v8.0.12

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-674CWE-776CWE-1333

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