Nodemailer before 10.0.9 Malformed Envelope Recipient via RFC 5322 Comment
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
Nodemailer is a Node.js email-sending library. In versions >= 9.1.0 and < 10.0.9, the address parser (src/addressparser) mishandles addresses whose local-part is a quoted string and that are followed by RFC 5322 comments, allowing trailing comment-separated domain atoms to be retained in the normalized address. For example, the input "user"@example.com(x)evil.com is parsed to the address value '[email protected] evil.com', which contains additional attacker-controlled domain text separated by a literal space. This parsed value is used without further strict recipient validation when the message envelope is built (envelope.to in src/mime-node), so a malformed/ambiguous recipient address can be accepted and placed in the SMTP envelope. Whether this results in delivery to an unintended recipient on real SMTP servers has not been confirmed. The issue is a variant of the RFC 5322 comment parsing problem addressed in GHSA-cc9r-2j5m-2m83, affecting the separate quoted-local-part code path. Version 10.0.9 contains a fix.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| nodemailer | nodemailer | 9.1.0 to before 10.0.9 | 10.0.9 | Patch available | CNA |
- nodemailer Vendornodemailer Affected 9.1.0 to before 10.0.9 Fixed in 10.0.9 Patch available CNA
Remediation
- Fix · CNA nodemailer (nodemailer) Fixed in 10.0.9
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 4 products
- Red Hat Developer Hub 1
- Red Hat Enterprise Linux 10
- Red Hat Hardened Images
- Self-service automation portal 2
Timeline
- 2026-10-02 Threatist record created from CVE-2026-100699
- 2026-10-03 Alias added: GHSA-fcjc-3m4q-q926
- 2026-10-27 Affected versions changed · Red Hat
References
More nodemailer vulnerabilities
- TI-2026-74559 ReDoS in Nodemailer SMTP AUTH mechanism detection regexes CVSS 4.0HIGH 8.7
- TI-2026-64856 nodemailer before 10.0.6 Denial of Service via addressparser CVSS 4.0HIGH 8.7
- TI-2026-62452 Nodemailer before 9.1.0 Denial of Service via addressparser CVSS 4.0HIGH 8.7
- TI-2026-61683 Nodemailer 9.1.0 through 10.0.4 Denial of Service via Quadratic Address Parsing CVSS 4.0HIGH 8.7
- TI-2025-13566 Nodemailer: nodemailer: denial of service via crafted email address header CVSS 3.1HIGH 7.5
- TI-2026-74560 Nodemailer address parser passes illegal characters to SMTP envelope CVSS 4.0MEDIUM 6.9
Sources
- CVE-2026-100699 · CVE Program
- CVE-2026-100699 · NVD
- FIRST EPSS
- GHSA-fcjc-3m4q-q926 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-100699 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences