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CVE-2026-33186 critical CVSS 9.1

Vulnerability in gRPC-Go (CVE-2026-33186)

Summary

Vulnerability in gRPC-Go (CVE-2026-33186). Confidential information can be exposed externally. Exploitable via info.FullMethod.

Original description

The description as published by the source.

gRPC-Go is the Go language implementation of gRPC. Versions prior to 1.79.3 have an authorization bypass resulting from improper input validation of the HTTP/2 :path pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the :path omitted the mandatory leading slash (e.g., Service/Method instead of /Service/Method). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official grpc/authz package) evaluated the raw, non-canonical path string. Consequently, "deny" rules defined using canonical paths (starting with /) failed to match the incoming request, allowing it to bypass the policy if a fallback "allow" rule was present. This affects gRPC-Go servers that use path-based authorization interceptors, such as the official RBAC implementation in google.golang.org/grpc/authz or custom interceptors relying on info.FullMethod or grpc.Method(ctx); AND that have a security policy contains specific "deny" rules for canonical paths but allows other requests by default (a fallback "allow" rule). The vulnerability is exploitable by an attacker who can send raw HTTP/2 frames with malformed :path headers directly to the gRPC server. The fix in version 1.79.3 ensures that any request with a :path that does not start with a leading slash is immediately rejected with a codes.Unimplemented error, preventing it from reaching authorization interceptors or handlers wi…

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

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-2026-33186 has been found in gRPC-Go.
Attackers can target a specific entry point like info.FullMethod over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 9.1/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "gRPC-Go CVE-2026-33186" on the vendor's site.

CVE-2026-33186 (gRPC-Go) — CWE-285 / CVSS v3 9.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: info.FullMethod / codes.Unimplemented
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-285) exists in gRPC-Go. Attackers reach the vulnerable code path via info.FullMethod without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of gRPC-Go. Attack surface: info.FullMethod / codes.Unimplemented.

🔥 Severity

Severity: Critical (CVSS 9.1/10). Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ 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 request patterns matching this CVE's known IOCs. Run grep -r 'gRPC-Go' . 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 'gRPC-Go' . | 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 gRPC-Go 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
    Post-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。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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