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.
CVE-2026-45133
HIGHNVD 7.57.5—
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit probability: 0.7%, top 49% 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: epss, nvd
7.5EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 7.5Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(medium)
- EG Risk
- 34(Track)EG Risk 34/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity75% × 45%Exploitation1% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 1%
- EPSS %ILE
- 51%
- KEV
- Not listed
Published
May 27, 2026
Last Modified
July 15, 2026
Advisory Details (5)
Auto-updated Jul 14, 2026Patch available. Sources: github_release, github.
github Patch Available
YAML Parser Stack Exhaustion via Unbounded Recursion in Nested Blocks, Sequences, and Mappings · Advisory · symfony/symfony · GitHub
https://github.com/symfony/symfony/security/advisories/GHSA-c2p3-7m5p-cv8xgithub_release Patch Available
v8.0.12
Patch available: symfony/symfony v8.0.12
https://github.com/symfony/symfony/releases/tag/v8.0.12github_release Patch Available
v7.4.12
Patch available: symfony/symfony v7.4.12
https://github.com/symfony/symfony/releases/tag/v7.4.12github_release Patch Available
v6.4.40
Patch available: symfony/symfony v6.4.40
https://github.com/symfony/symfony/releases/tag/v6.4.40github_release Patch Available
v5.4.52
Patch available: symfony/symfony v5.4.52
https://github.com/symfony/symfony/releases/tag/v5.4.52Vendor Advisories for CVE-2026-45133(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)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| symfony/symfony | v8.0.0 ... v8.0.9 (12 versions) | 8.0.12 | — |
| symfony/yaml | v8.0.0 ... v8.0.8 (6 versions) | 8.0.12 | — |
Weakness Classification(3)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 18× 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.
- 2026-07-27 09:57 UTCEG score recompute
- 2026-07-26 14:54 UTCEPSS rescore
- 2026-07-26 14:54 UTCEPSS rescore
- 2026-07-25 14:18 UTCEPSS rescore
- 2026-07-24 14:17 UTCEPSS rescore
- 2026-07-23 14:18 UTCEPSS rescore
- 2026-07-23 03:16 UTCEG score recompute▼ 0.70
- 2026-07-22 14:08 UTCEPSS rescore
- 2026-07-21 15:24 UTCEPSS rescore
- 2026-07-20 17:08 UTCEPSS rescore
- 2026-07-19 14:31 UTCEPSS rescore
- 2026-07-19 02:29 UTCEPSS rescore
- 2026-07-18 10:04 UTCEPSS rescore
- 2026-07-16 17:03 UTCEPSS rescore
- 2026-07-15 16:57 UTCEPSS rescore
- 2026-07-15 16:23 UTCNVD updateCVSS v3 → 7.5
- 2026-07-14 19:04 UTCEG score recompute▲ 8.20
- 2026-07-14 19:00 UTCMITRE cvelistV5CVSS v3 → 8.2 · CVSS v4 → 8.2 · severity → HIGH
- 2026-06-14 23:18 UTCEPSS rescore
- 2026-06-13 23:00 UTCEPSS rescore
- 2026-06-12 23:12 UTCEPSS rescore
- 2026-05-27 21:35 UTCEG score recompute
Frequently asked(5)
What is CVE-2026-45133?
CVE-2026-45133 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, when the parser is exposed to attacker-controlled input, deeply nested mappings or sequences cause both the block-level (Parser::parseBlock()) and inline…
When was CVE-2026-45133 disclosed?
CVE-2026-45133 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-2026-45133 actively exploited?
CVE-2026-45133 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 49.1% of all scored CVEs.
What is the CVSS score of CVE-2026-45133?
CVE-2026-45133 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-45133?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-45133, 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
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-45133
Is Your Infrastructure Affected by CVE-2026-45133?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.