CVE-2026-45304

Symfony: YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs")

HIGH

7.5

CVSS Score

Published: July 14, 2026 at 06:48 PM UTC

Updated: July 15, 2026 at 03:14 PM UTC

3 products affected across 2 vendorsSymfonySymfonyYaml

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Severity

HIGH7.5

Exploit prediction

EPSS 0.7%

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, Symfony\Component\Yaml\Parser resolved YAML collection aliases recursively, allowing a small untrusted YAML input to expand into a multi-gigabyte structure and exhaust memory. 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

Yaml · Symfony

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 (6)

x_refsource_CONFIRMPatchVendor Advisory

Source: cverecord

https://github.com/symfony/symfony/security/advisories/GHSA-4qpc-3hr4-r2p4

x_refsource_MISCPatch

Source: cverecord

https://github.com/symfony/symfony/commit/e77391b2e4f18821198f010d573674c8ed4a970a

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 exploitAutomatablePartial 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-776

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