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CVE-2026-90776 high CVSS 7.5

Vulnerability in nodemailer (CVE-2026-90776)

Summary

Vulnerability in nodemailer (CVE-2026-90776). Risk of unauthorized operations or information disclosure. Exploitable via addressparser. Mitigation: upgrade to 10.0.5 or later.

Original description

The description as published by the source.

Summary

nodemailer/lib/addressparser parses one shape of address in O(n^2) time. A single ~640 KB address value blocks the Node.js event loop for roughly 7 seconds. And it is reachable without auth: mailparser feeds inbound email headers straight into this parser, so one crafted email is enough to stall a service that parses mail.

Details

The parser builds a single address by accumulating its atoms into one string. When the atoms are separated by RFC 5322 comments, like a@b(c)@b(c)@b(c)..., every atom re-joins that same growing string.

The join check in src/addressparser/index.ts:

const joins =
    prevToken &&
    prevToken.noBreak &&
    parts.length &&
    (prevToken.value !== ')' || parts[parts.length - 1].slice(-1) === '@' || token.value.charAt(0) === '@');

The issue is the order of the last two operands. parts[parts.length - 1].slice(-1) runs before the cheap token.value.charAt(0). slice(-1) has to flatten the accumulator to read its last character → O(current length) → and that runs on every token → O(n^2) over the whole value. Since || is left to right, the cheap charAt(0) that would short-circuit never gets the chance.

The chain: long comment-joined address → one growing accumulator → slice(-1) re-flattens it on every token → quadratic parse time.

PoC

Isolated, just the parser (npm i nodemailer@10.0.3):

const addressparser = require('nodemailer/lib/addressparser');
const s = Date.now();
addressparser('a' + '@b…

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-2026-90776 has been found in nodemailer.
Attackers can target a specific entry point like addressparser over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade nodemailer to 10.0.5 or later.
If unsure, ask your IT team or search "nodemailer CVE-2026-90776" on the vendor's site.

CVE-2026-90776 (nodemailer) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: addressparser / From
Patched: 10.0.5 — 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.

❓ What is the problem

A vulnerability (CWE-400) exists in nodemailer. Attackers reach the vulnerable code path via addressparser without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of nodemailer. Attack surface: addressparser / From.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 10.0.5.

🛡️ 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 'nodemailer' . 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 'nodemailer' . | 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 nodemailer 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
    Apply patch patch 
    Upgrade nodemailer to 10.0.5

    ステージング環境で 10.0.5 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。

  3. 3
    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。

Affected packages

npm nodemailer
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"10.0.5"}]}]

References

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