vulnerability / NVI-00013996 / Revision 1
Nodemailer: Recipient-domain validation bypass via RFC 5322 comment mis-parsing leads to email delivery to an attacker-controlled domain
GitHub lists this reviewed advisory for nodemailer. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.5 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
nodemailer
source listed>= 6.9.16, < 9.1.0
### Summary Nodemailer's email-address parser treats an **RFC 5322 comment** `( ... )` inside the domain as a point to **concatenate** the surrounding text, rather than as folding whitespace (CFWS) that **terminates** the domain. Consequently a recipient address such as `user@good-corp.com(x)evil.com` is parsed and **delivered to `good-corp.comevil.com`** (registrable domain `comevil.com`, attacker‑controlled), while a conformant RFC 5322 parser terminates the domain at the comment and reads `good-corp.com`. An application that decides *whether it is allowed to email a recipient* by parsing/validating the recipient's domain — with a strict RFC 5322 parser (used without inspecting parse defects) or with a naive prefix/substring allow‑list — and then hands the raw address to Nodemailer for delivery, can be induced to send mail to a domain the attacker controls. This is an **Interpretation Conflict (CWE‑436)**, the same class as CVE‑2025‑13033, reached through the RFC 5322 *comment* construct (the "Comments" technique in PortSwigger's *Splitting the email atom* research, which produced a Postfix fix). Severity is **Moderate**: exploitation requires the app's domain check to disagre
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
A fixed release is not deployment evidence.
Check current vendor support and compatibility. After making a change, verify the deployed build and relevant runtime conditions. Keep the evidence, owner and time. An updated lockfile alone does not prove what is running.
04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-cc9r-2j5m-2m83 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.