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CVE-2026-55637

Vulnerability in github.com/geiserx/genieacs-mcp (CVE-2026-55637)

Summary

Vulnerability in github.com/geiserx/genieacs-mcp (CVE-2026-55637). Risk of unauthorized operations or information disclosure. Exploitable via POST /mcp. Mitigation: upgrade to 0.3.2 or later.

Original description

The description as published by the source.

genieacs-mcp exposes a local Streamable HTTP MCP endpoint that accepts attacker-controlled Host and Origin headers. A malicious web page can use DNS rebinding to route browser requests to a victim's loopback MCP listener while preserving the attacker origin. The server accepts the request, initializes an MCP session, lists GenieACS tools, and can invoke tools against the configured GenieACS NBI without a browser-supplied secret.

The affected package is genieacs-mcp version 0.3.1 at commit 4d7d3c74740efb7f3833aadc8a8e9177650eb462.

The vulnerable transport setup is in cmd/server/main.go. When TRANSPORT is not stdio, the server creates a Streamable HTTP MCP handler:

// cmd/server/main.go:92
httpSrv := server.NewStreamableHTTPServer(s)
addr := os.Getenv("MCP_LISTEN_ADDR")
if addr == "" {
    addr = "127.0.0.1:8080"
}
authToken := os.Getenv("MCP_AUTH_TOKEN")
if authToken == "" && !isLoopbackAddr(addr) {
    log.Fatal("MCP_AUTH_TOKEN is required when MCP_LISTEN_ADDR is not loopback")
}
if authToken != "" {
    mux := http.NewServeMux()
    mux.Handle("/mcp", bearerAuth(httpSrv, authToken))
    log.Printf("GenieACS MCP bridge listening on %s (auth enabled)", addr)
    if err := http.ListenAndServe(addr, mux); err != nil {
        log.Fatalf("server error: %v", err)
    }
} else {
    log.Printf("GenieACS MCP bridge listening on %s", addr)
    if err := httpSrv.Start(addr); err != nil {
        log.Fatalf("server error: %v", err)
    }
}

For the defaul…

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-2026-55637 has been found in github.com/geiserx/genieacs-mcp.
Attackers can target a specific entry point like POST /mcp over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade github.com/geiserx/genieacs-mcp to 0.3.2 or later.
If unsure, ask your IT team or search "github.com/geiserx/genieacs-mcp CVE-2026-55637" on the vendor's site.

CVE-2026-55637 (github.com/geiserx/genieacs-mcp) — CWE-346
Attack surface: POST /mcp / Host / Origin / TRANSPORT
Patched: 0.3.2 — 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-346) exists in github.com/geiserx/genieacs-mcp. Attackers reach the vulnerable code path via POST /mcp.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/geiserx/genieacs-mcp. Attack surface: POST /mcp / Host / Origin / TRANSPORT.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 0.3.2.

🛡️ 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 POST /mcp requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/geiserx/genieacs-mcp' . 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/geiserx/genieacs-mcp' . | 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/geiserx/genieacs-mcp 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 'POST /mcp' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'

    アクセスログで POST /mcp 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/geiserx/genieacs-mcp to 0.3.2

    ステージング環境で 0.3.2 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 POST /mcp 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/geiserx/genieacs-mcp
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.3.2"}]}]

References

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