# CVE-2026-100700: nodemailer before 10.0.6 Denial of Service via addressparser

> Attackers can cause service unavailability in applications using nodemailer by sending crafted email headers that trigger quadratic backtracking in the address parser.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 26 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** CLEANSTART-2026-TF67496, CLEANSTART-2026-UX56548, CLSA-2026-1790863073, CLSA-2026-1790937712, CLSA-2026-1791028046, DEBIAN-CVE-2026-100700, ECHO-cde4-c12a-3080, GHSA-c7vw-frhj-6h9j, GHSA-v53p-9fqp-m79j, MINI-3v92-j972-3cq5, MINI-4mfg-xm9f-g69m, MINI-6fh4-7ff5-38gc, MINI-6wrh-5rg4-5fcg, MINI-7hx9-34jg-gvfm, MINI-7rf7-4vfr-53mx, MINI-cfw7-g8w3-qmxg, MINI-fj6v-r6rv-c5cq, MINI-fvjh-8q3p-jrg3, MINI-gqwj-pvj8-3hpg, MINI-gxf5-xqhg-r893, MINI-hwx9-x866-5j2q, MINI-mpw8-mhpp-jmj4, MINI-rp6f-ghg6-9v2w, MINI-v4p4-8gvq-j72w, ROOT-APP-NPM-GHSA-v53p-9fqp-m79j, UBUNTU-CVE-2026-100700

## What is CVE-2026-100700?

CVE-2026-100700 is a high-severity denial of service vulnerability in nodemailer, published on 26 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

nodemailer before 10.0.6 contains a denial of service vulnerability in the addressparser free-text fallback regex pattern that exhibits quadratic backtracking behavior. Attackers can supply crafted email header values with long whitespace-free runs to block the Node.js event loop for tens of seconds, causing service unavailability.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-100700?

2 open source packages ship an affected version, including nodemailer.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nodemailer` | npm | All versions | 10.0.6 |
| `nodemailer` | npm | All versions | 10.0.6 |

## How do I fix CVE-2026-100700?

Upgrade nodemailer to 10.0.6 or later.

## Is CVE-2026-100700 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100700 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100700 and fix it if it is affected.

What it is: CVE-2026-100700 is a high-severity denial of service vulnerability in nodemailer, published on 26 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100700 exists.

Affected packages and fixed versions:
- nodemailer (npm): affected all versions; fixed in 10.0.6
- nodemailer (npm): affected all versions; fixed in 10.0.6

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-100700/ (Markdown: https://insights.sbomify.com/CVE-2026-100700/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100700
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100700
- OSV: https://osv.dev/vulnerability/CVE-2026-100700

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100700/
Summaries are generated and may contain mistakes; the official description above is the record.