Netty SMTP CMD Injection via CRLF in DefaultSmtpRequest (4.1.128/4.2.7)
CVE-2025-59419 Published on October 15, 2025
Netty netty-codec-smtp SMTP Command Injection Vulnerability Allowing Email Forgery
Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.128.Final and 4.2.7.Final, the SMTP codec in Netty contains an SMTP command injection vulnerability due to insufficient input validation for Carriage Return (\r) and Line Feed (\n) characters in user-supplied parameters. The vulnerability exists in io.netty.handler.codec.smtp.DefaultSmtpRequest, where parameters are directly concatenated into the SMTP command string without sanitization. When methods such as SmtpRequests.rcpt(recipient) are called with a malicious string containing CRLF sequences, attackers can inject arbitrary SMTP commands. Because the injected commands are sent from the server's trusted IP address, resulting emails will likely pass SPF and DKIM authentication checks, making them appear legitimate. This allows remote attackers who can control SMTP command parameters (such as email recipients) to forge arbitrary emails from the trusted server, potentially impersonating executives and forging high-stakes corporate communications. This issue has been patched in versions 4.1.129.Final and 4.2.8.Final. No known workarounds exist.
Weakness Type
What is a CRLF Injection Vulnerability?
The software uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.
CVE-2025-59419 has been classified to as a CRLF Injection vulnerability or weakness.
Products Associated with CVE-2025-59419
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Affected Versions
netty:- Version < 4.2.7.Final is affected.
- Version >= 4.2.0.Alpha1, < 4.1.128.Final is affected.
Vulnerable Packages
The following package name and versions may be associated with CVE-2025-59419
| Package Manager | Vulnerable Package | Versions | Fixed In |
|---|---|---|---|
| maven | io.netty:netty-codec-smtp | >= 4.2.0.Alpha1, < 4.2.7.Final | 4.2.7.Final |
| maven | io.netty:netty-codec-smtp | < 4.1.128.Final | 4.1.128.Final |
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.