CVE-2026-45304

HIGHNVD 7.58.7
EchelonGraph scoreLOW confidence

This high-severity CVE scores 8.7 under the CNA's CVSS (NVD's own analysis pending). EPSS exploit probability: 0.1%, top 77% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: cna:github_m, epss
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
7.5
EG Score
8.7(low)
EG Risk
—
EPSS
52.9%
KEV
Not listed

Published

May 27, 2026

Last Modified

July 15, 2026

Advisory Details (6)

Auto-updated Jul 14, 2026
Patch available. Sources: github_commit, github_release, github.
github Patch Available

YAML Parser Exponential Memory Allocation via Recursive Collection-Alias Expansion ("Billion Laughs") · Advisory · symfony/symfony · GitHub

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

v8.0.12

Patch available: symfony/symfony v8.0.12

https://github.com/symfony/symfony/releases/tag/v8.0.12
github_release Patch Available

v7.4.12

Patch available: symfony/symfony v7.4.12

https://github.com/symfony/symfony/releases/tag/v7.4.12
github_release Patch Available

v6.4.40

Patch available: symfony/symfony v6.4.40

https://github.com/symfony/symfony/releases/tag/v6.4.40
github_release Patch Available

v5.4.52

Patch available: symfony/symfony v5.4.52

https://github.com/symfony/symfony/releases/tag/v5.4.52
github_commit Patch Available

commit e77391b2e4f1 (symfony/symfony)

Patch available: symfony/symfony v5.4.52 (contains commit e77391b2e4f1)

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

Vendor Advisories for CVE-2026-45304(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(2 across 1 ecosystem)
Packagist(2)
PackageVulnerable rangeFixed inDependents
symfony/symfonyv8.0.0 ... v8.0.9 (12 versions)8.0.12—
symfony/yamlv8.0.0 ... v8.0.8 (6 versions)8.0.12—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 11× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:24 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 02:29 UTCEPSS rescore
  6. 2026-07-18 10:04 UTCEPSS rescore
  7. 2026-07-16 17:03 UTCEPSS rescore
  8. 2026-07-15 16:57 UTCEPSS rescore
  9. 2026-07-15 16:23 UTCNVD updateCVSS v3 → 7.5
  10. 2026-07-14 19:03 UTCEG score recompute▲ 8.70
  11. 2026-07-14 19:00 UTCMITRE cvelistV5CVSS v3 → 8.7 · CVSS v4 → 8.7 · severity → HIGH
  12. 2026-06-14 23:18 UTCEPSS rescore
  13. 2026-06-13 23:00 UTCEPSS rescore
  14. 2026-06-12 23:12 UTCEPSS rescore
  15. 2026-05-27 21:35 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-45304?
CVE-2026-45304 is a high vulnerability published on May 27, 2026. 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…
When was CVE-2026-45304 disclosed?
CVE-2026-45304 was first published in the National Vulnerability Database on May 27, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-45304 actively exploited?
CVE-2026-45304 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 52.9% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-45304?
CVE-2026-45304 has a CVSS v3 base score of 7.5 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.7. The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-45304?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-45304, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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