# CVE-2026-92597: Nodemailer before 9.1.0 Email Domain Validation Bypass via RFC 5322 Comment

> Attackers can bypass email domain validation to deliver mail to attacker-controlled domains by exploiting RFC 5322 comment parsing flaws in Nodemailer.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/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:** 16 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** CLEANSTART-2026-MX71943, CLEANSTART-2026-NF96877, CLEANSTART-2026-ZC19840, DEBIAN-CVE-2026-92597, ECHO-caa4-97bc-c181, GHSA-8pjj-q6q6-qm29, GHSA-cc9r-2j5m-2m83, MINI-78w2-wfwh-995v, MINI-846x-x8jw-2fm4, MINI-9xw3-3p7p-g9gq, MINI-c43v-hcmx-6wqh, MINI-fr7m-6p43-99ph, MINI-gqjv-hwcm-mf7w, MINI-h46v-f28c-c847, MINI-hxfv-r86c-ccw6, MINI-r75g-xrmv-9qm9, MINI-rxw9-mf7m-9hcr, MINI-wcqc-qx8h-8vwh, UBUNTU-CVE-2026-92597

## What is CVE-2026-92597?

CVE-2026-92597 is a high-severity vulnerability in nodemailer, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Nodemailer versions >= 6.9.16 and < 9.1.0 mis-parse RFC 5322 comments in email addresses: in lib/addressparser, a comment closed immediately before a non-break character causes the tokenizer to concatenate the atoms surrounding the comment instead of treating the comment as folding whitespace that terminates the domain. A recipient address such as user@good-corp.com(x)evil.com is therefore read by Nodemailer as the single domain good-corp.comevil.com (registrable domain comevil.com, which an attacker can register) and used for both the SMTP envelope (RCPT TO) and the emitted To:/From: headers, while a conformant RFC 5322 parser terminates the domain at the comment and reads good-corp.com. An application that validates the recipient domain with a strict RFC 5322 parser (without inspecting parse defects) or a naive prefix/substring allow-list and then hands the raw address to Nodemailer can be induced to deliver mail to a domain the attacker controls. Fixed in 9.1.0.

Weakness: CWE-436 (Interpretation Conflict)

## Which versions are affected by CVE-2026-92597?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nodemailer` | npm | From 6.9.16 | 9.1.0 |
| `nodemailer` | npm | From 6.9.16 | 9.1.0 |

## How do I fix CVE-2026-92597?

Upgrade nodemailer to 9.1.0 or later.

## Is CVE-2026-92597 being exploited?

There is no known exploitation of CVE-2026-92597 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-92597 and fix it if it is affected.

What it is: CVE-2026-92597 is a high-severity vulnerability in nodemailer, published on 16 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-92597 in the wild and no public exploit code.

Affected packages and fixed versions:
- nodemailer (npm): affected from 6.9.16; fixed in 9.1.0
- nodemailer (npm): affected from 6.9.16; fixed in 9.1.0

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-2026-92597/ (Markdown: https://insights.sbomify.com/CVE-2026-92597/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-92597
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-92597
- OSV: https://osv.dev/vulnerability/CVE-2026-92597

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-92597/
Summaries are generated and may contain mistakes; the official description above is the record.