SMTP command smuggling via unvalidated command names
Published Sep 18, 2026 · Updated Sep 18, 2026
CRLF injection in Netty netty-codec-smtp allows remote attackers to smuggle SMTP commands through an untrusted command name. SmtpCommand.valueOf accepts CR and LF without validation, and SmtpRequestEncoder writes the resulting command verbatim into the SMTP byte stream. Exploitation requires application code to place untrusted data in the normally fixed command-name field, enabling unauthorized relay or forged sender and recipient commands.
Summary
What happened
CRLF injection in Netty netty-codec-smtp allows remote attackers to smuggle SMTP commands through an untrusted command name. SmtpCommand.valueOf accepts CR and LF without validation, and SmtpRequestEncoder writes the resulting command verbatim into the SMTP byte stream. Exploitation requires application code to place untrusted data in the normally fixed command-name field, enabling unauthorized relay or forged sender and recipient commands.
The record
- CVE
- CVE-2026-93576
- Published
- Sep 18, 2026
- Updated
- Sep 18, 2026
- Vendor
- Commonhaus Foundation
- Product
- Red Hat JBoss Enterprise Application Platform 7
- Classifications
- CWE-93
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 18, 2026CVE publishedPublication date reported by the CVE source.
- Sep 18, 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?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
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.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
- Netty SMTP command-name EmbeddedChannel reproductionproof of concept · demonstrated
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Technologies
Your stack
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