SMTP command injection via unsanitized envelope size
Published Aug 31, 2026 · Updated Aug 31, 2026
SMTP command injection in Nodemailer before 8.0.4 allows remote authenticated users to add hidden email recipients. In lib/smtp-connection/index.js, the MAIL FROM builder appends envelope.size after SIZE= without neutralizing CRLF, so injected text becomes new SMTP commands. Exploitation requires an application to pass attacker-controlled size in a custom envelope; the default envelope omits it, and successful RCPT TO injection copies outgoing mail to a hidden recipient.
Summary
What happened
SMTP command injection in Nodemailer before 8.0.4 allows remote authenticated users to add hidden email recipients. In lib/smtp-connection/index.js, the MAIL FROM builder appends envelope.size after SIZE= without neutralizing CRLF, so injected text becomes new SMTP commands. Exploitation requires an application to pass attacker-controlled size in a custom envelope; the default envelope omits it, and successful RCPT TO injection copies outgoing mail to a hidden recipient.
The record
- CVE
- CVE-2026-82854
- Published
- Aug 31, 2026
- Updated
- Aug 31, 2026
- Vendor
- Nodemailer
- Product
- Nodemailer
- Classifications
- CWE-93, CAPEC-15, T1565.002
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 31, 2026CVE publishedPublication date reported by the CVE source.
- Aug 31, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <8.0.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream SMTP command injection proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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