CVE-2026-100699

MEDIUMPre-NVD 5.35.3—
EchelonGraph scoreHIGH confidence

Score 5.3 from GitHub Security Advisory published 2026-09-26. A secondary CVSS source baseline 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this weekElevated
5.3EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 5.3Exploit: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
5.3
EG Score
5.3MEDIUMhigh confidence
EG Risk
55
EG Risk 55/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity53% × 45%
Exploitation40% × 40%
Automatability100% × 15%
CISA SSVC: Track at low or medium mission impact; Attend at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
EPSS PROB
0.2%
EPSS %ILE
8th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Attend at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.

Exploitation public PoC (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

September 26, 2026

Last Modified

September 30, 2026

Advisory Details (2)

Auto-updated Sep 26, 2026
Patch available. Sources: github.
generic

Nodemailer before 10.0.9 Malformed Envelope Recipient via RFC 5322 Comment | Advisories | VulnCheck

https://www.vulncheck.com/advisories/nodemailer-before-10.0.9-malformed-envelope-recipient-via-rfc-5322-comment
github Patch Available

Quoted local-part can produce malformed envelope recipient through RFC 5322 comment parsing · Advisory · nodemailer/nodemailer · GitHub

https://github.com/nodemailer/nodemailer/security/advisories/GHSA-g57g-f23g-4646

Vendor Advisories for CVE-2026-100699(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
nodemailer—10.0.9—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 20× in last 7d / 23× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-10-03 22:45 UTCEG score recompute
  2. 2026-10-03 22:45 UTCGHSA enrichment
  3. 2026-10-03 14:25 UTCEPSS rescore
  4. 2026-10-02 20:46 UTCEG score recompute
  5. 2026-10-02 20:46 UTCGHSA enrichment
  6. 2026-10-01 19:49 UTCEPSS rescore
  7. 2026-10-01 18:46 UTCGHSA enrichment
  8. 2026-09-30 16:44 UTCEG score recompute
  9. 2026-09-30 16:44 UTCGHSA enrichment
  10. 2026-09-30 15:02 UTCEPSS rescore
  11. 2026-09-29 20:20 UTCEG score recompute
  12. 2026-09-29 20:20 UTCGHSA enrichment
  13. 2026-09-29 15:20 UTCEPSS rescore
  14. 2026-09-28 18:21 UTCEG score recompute
  15. 2026-09-28 18:21 UTCGHSA enrichment
  16. 2026-09-28 17:50 UTCEG score recompute
  17. 2026-09-28 17:49 UTCGHSA enrichment
  18. 2026-09-28 13:50 UTCEPSS rescore
  19. 2026-09-27 16:28 UTCEG score recompute
  20. 2026-09-27 16:28 UTCGHSA enrichment
  21. 2026-09-26 14:29 UTCEG score recompute
  22. 2026-09-26 13:35 UTCEG score recompute
  23. 2026-09-26 13:30 UTCMITRE cvelistV5first tracked

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-100699?
CVE-2026-100699 is a medium vulnerability published on September 26, 2026. 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…
When was CVE-2026-100699 disclosed?
CVE-2026-100699 was first published on September 26, 2026, with the most recent update on September 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-100699 actively exploited?
CVE-2026-100699 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (8th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-100699?
CVE-2026-100699 has a CVSS base score of 5.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-100699?
A fix for CVE-2026-100699 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-100699 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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