Vulnerability in webonyx/graphql-php (CVE-2026-40476)
Summary
Vulnerability in webonyx/graphql-php (CVE-2026-40476). Risk of unauthorized operations or information disclosure. Exploitable via OverlappingFieldsCanBeMerged. Mitigation: upgrade to 15.31.5 or later.
Original description
The description as published by the source.
The OverlappingFieldsCanBeMerged validation rule exhibits quadratic time complexity when processing queries with many repeated fields sharing the same response name. An attacker can send a crafted query like { hello hello hello ... } with thousands of repeated fields, causing excessive CPU usage during validation before execution begins.
This is not mitigated by existing QueryDepth or QueryComplexity rules.
Observed impact (tested on v15.31.4):
- 1000 fields: ~0.6s
- 2000 fields: ~2.4s
- 3000 fields: ~5.3s
- 5000 fields: request timeout (>20s)
Root cause: collectConflictsWithin() performs O(n²) pairwise comparisons of all fields with the same response name. For identical repeated fields, every comparison returns "no conflict" but the quadratic iteration count causes resource exhaustion.
Fix: Deduplicate structurally identical fields before pairwise comparison, reducing the complexity from O(n²) to O(u²) where u is the number of unique field signatures (typically 1 for this attack pattern).
Credit: Ashwak N (ashwakn04@gmail.com)
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-40476 has been found in webonyx/graphql-php.
Attackers can target a specific entry point like OverlappingFieldsCanBeMerged over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade webonyx/graphql-php to 15.31.5 or later.
If unsure, ask your IT team or search "webonyx/graphql-php CVE-2026-40476" on the vendor's site.
CVE-2026-40476 (webonyx/graphql-php) — CWE-407 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: OverlappingFieldsCanBeMerged
Patched: 15.31.5 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-407) exists in webonyx/graphql-php. Attackers reach the vulnerable code path via OverlappingFieldsCanBeMerged without authentication.
Check the vendor advisory for the affected versions of webonyx/graphql-php. Attack surface: OverlappingFieldsCanBeMerged.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 15.31.5.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'webonyx/graphql-php' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'webonyx/graphql-php' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
webonyx/graphql-phpを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade webonyx/graphql-php to 15.31.5ステージング環境で 15.31.5 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- patch security-advisories@github.com
- web security-advisories@github.com
- web github.com
- web openwall.com