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CVE-2026-100347 medium CVSS 5.3

Vulnerability in github.com/getkin/kin-openapi (CVE-2026-100347)

Summary

Vulnerability in github.com/getkin/kin-openapi (CVE-2026-100347). Risk of unauthorized operations or information disclosure. Exploitable via get /ping. Mitigation: upgrade to 0.145.0 or later.

Original description

The description as published by the source.

Summary

The openapi3filter.ValidationHandler (the exported, documented request-validation middleware) hard-wires the legacy router (routers/legacy). That router matches the incoming request method verbatim against a trie built exclusively from upper-cased canonical HTTP methods. A request carrying a method token that is not one of the 9 standard methods — a legitimate-but-unsupported token such as PROPFIND, or a non-canonical case variant such as lowercase get — misses the trie, leaves route == nil, and for an existing static path falls through to PathItem.GetOperation(method), whose default: case calls panic(...). The panic fires inside route resolution, before any authentication runs. This is an unauthenticated, remotely triggerable denial of service (recovered per-connection panic + unbounded error-log growth).

Root Cause

  • openapi3filter/validation_handler.go:39 — ValidationHandler.Load() always constructs legacyrouter.NewRouter(doc); there is no alternative router option on this path.
  • routers/legacy/router.go:109 — the request method is used verbatim (method, url := req.Method, ...); there is no canonicalization or rejection of unknown method tokens.
  • routers/legacy/router.go:69-70 — the trie is populated with strings.ToUpper(method) keys taken from pathItem.Operations() (canonical http.Method* constants only).
  • routers/legacy/router.go:141 — root.Match(method + " " + remainingPath) misses for a non-canonical/unsup…

Source: GitHub Security Advisories (Global) 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-2026-100347 has been found in github.com/getkin/kin-openapi.
Attackers can target a specific entry point like get /ping over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade github.com/getkin/kin-openapi to 0.145.0 or later.
If unsure, ask your IT team or search "github.com/getkin/kin-openapi CVE-2026-100347" on the vendor's site.

CVE-2026-100347 (github.com/getkin/kin-openapi) — CWE-20 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: get /ping / GET /ping / openapi3filter.ValidationHandler / PROPFIND
Patched: 0.145.0 — 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.

❓ What is the problem

A vulnerability (CWE-20) exists in github.com/getkin/kin-openapi. Attackers reach the vulnerable code path via get /ping without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/getkin/kin-openapi. Attack surface: get /ping / GET /ping / openapi3filter.ValidationHandler / PROPFIND.

🔥 Severity

Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 0.145.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual GET /ping requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/getkin/kin-openapi' . 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

  1. 1
    Identify exposure identify 
    grep -r 'github.com/getkin/kin-openapi' . | 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 github.com/getkin/kin-openapi を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Hunt for indicators of compromise detect 
    grep 'GET /ping' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで GET /ping への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。

  3. 3
    Apply patch patch 
    Upgrade github.com/getkin/kin-openapi to 0.145.0

    ステージング環境で 0.145.0 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と、Step 2 で見つけた異常検知の続報チェックを含めること。

  4. 4
    Post-deployment verification verify 
    Replay attack against GET /ping on staging to confirm patch closes the vector

    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 Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

go github.com/getkin/kin-openapi
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.145.0"}]}]

References

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