How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

394,002

Total vulnerabilities in the database

Nodemailer addressparser: O(n^2) on comment-joined addresses enables a remote DoS (reachable via mailparser) — nodemailer

Uncontrolled Resource Consumption

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 &amp;&amp;
    prevToken.noBreak &amp;&amp;
    parts.length &amp;&amp;
    (prevToken.value !== &#039;)&#039; || parts[parts.length - 1].slice(-1) === &#039;@&#039; || token.value.charAt(0) === &#039;@&#039;);

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 [email protected]):

const addressparser = require(&#039;nodemailer/lib/addressparser&#039;);
const s = Date.now();
addressparser(&#039;a&#039; + &#039;@b(c)&#039;.repeat(130000));
console.log(Date.now() - s, &#039;ms&#039;); // ~7000 ms, blocking

End to end through mailparser, the remote path (npm i [email protected]):

const { simpleParser } = require(&#039;mailparser&#039;);
(async () =&gt; {
  const to = &#039;a&#039; + &#039;@b(c)&#039;.repeat(130000);
  const eml = `From: [email protected]\r\nTo: ${to}\r\nSubject: x\r\n\r\nhi\r\n`;
  const s = Date.now();
  await simpleParser(eml);
  console.log(Date.now() - s, &#039;ms&#039;); // ~7000 ms, blocking
})();

Timings measured on 10.0.3:

| Address value | Parse time | | --- | --- | | 390 KB | 1.3 s | | 585 KB | 5.6 s | | 640 KB | 6.7 s | | 976 KB | 18 s |

It survives RFC 5322 folding: fold the header at offsets that are a multiple of the atom length and every )+@ junction stays intact, so the payload is a standards-compliant email with lines under 998 octets and still triggers it.

Impact

Algorithmic-complexity DoS. Node is single threaded, so the block stalls everything else in the process, and a handful of these back to back keeps a service down.

Affected: anything that runs addressparser on attacker-controlled input, either the public export directly or address headers built from user input. The unauthenticated remote case is mailparser. 3.9.24 pins nodemailer 10.0.3 and calls the parser on inbound To/From/Cc with no length cap, so any service parsing inbound mail with it can be frozen by a single email.

Suggested fix

Swap the last two operands so the cheap check runs first:

(prevToken.value !== &#039;)&#039; || token.value.charAt(0) === &#039;@&#039; || parts[parts.length - 1].slice(-1) === &#039;@&#039;)

Pure boolean commutation, so the parse output is identical. Verified byte for byte on the test inputs, and the full 1276-test suite passes.

Published: Sep 30, 2026
Updated: Oct 6, 2026
GHSA: GHSA-prgh-xp8r-p3m5
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: High
Score: 7.5
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWEs:

Affected Software
References

Software	Affected versions
nodemailer	`>= 9.1.0, < 10.0.5`

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.