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CVE-2026-38728
high
CVSS 7.5
Vulnerability in smtp-server (CVE-2026-38728)
Summary
vulnerability in smtp-server (CVE-2026-38728). Risk of unauthorized operations or information disclosure. Exploitable via ``_remainder``. Mitigation: upgrade to `3.18.3` or later.
AI summary snake-internal / snake-material-v2
A vulnerability tracked as **CVE-2026-38728** has been found in smtp-server.
Attackers can target a specific entry point like ``_remainder`` over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade smtp-server to **3.18.3** or later.
If unsure, ask your IT team or search "smtp-server CVE-2026-38728" on the vendor's site.
CVE-2026-38728 (smtp-server) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: `_remainder` / `SMTPStream._write` / `_write` / `this._remainder`
Patched: `3.18.3` — 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-400) exists in smtp-server. Attackers reach the vulnerable code path via ``_remainder`` without authentication.
📍 Affected scope
smtp-server — . Attack surface: `_remainder` / `SMTPStream._write` / `_write` / `this._remainder`.
🔥 Severity
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure
🔧 How to fix
Update to **3.18.3**.
🛡️ 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 'smtp-server' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response Actions (7 steps)
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'smtp-server' . | 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 `smtp-server` を grep し、稼働しているサービス・バージョンを把握する。
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6Apply patch patch
Upgrade smtp-server to 3.18.3ステージング環境で 3.18.3 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 3 で見つけた異常検知の続報チェックを含めること。
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7Post-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 Step 3 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
npm
smtp-server
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.18.3"}]}]
References
- web https://nvd.nist.gov/vuln/detail/CVE-2026-38728
- web https://bytecreator.dev/blog/CVE-2026-38728
- web https://github.com/nodemailer/smtp-server
- web https://github.com/nodemailer/smtp-server/releases/tag/v3.18.3
- web https://github.com/advisories/GHSA-fv2f-rw9f-v9cm
- web https://github.com/nodemailer/smtp-server/commit/592c5666fa0c76d1d04c1a32abad0ef806fbfe97