Netty prior 4.1.128.Final/4.2.7.Final io.netty.handler.codec.smtp.DefaultSmtpRequest crlf injection

Summaryinfo

A vulnerability identified as problematic has been detected in Netty. This affects an unknown part of the component io.netty.handler.codec.smtp.DefaultSmtpRequest. The manipulation leads to crlf injection. This vulnerability is referenced as CVE-2025-59419. Remote exploitation of the attack is possible. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Netty. It has been rated as problematic. This issue affects some unknown functionality of the component io.netty.handler.codec.smtp.DefaultSmtpRequest. The manipulation with an unknown input leads to a crlf injection vulnerability. Using CWE to declare the problem leads to CWE-93. The product 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. Impacted is integrity. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2025-59419 since 09/15/2025. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 4.1.128.Final or 4.2.7.Final eliminates this vulnerability. Applying the patch 1782e8c2060a244c4d4e6f9d9112d5517ca05120 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at EUVD (EUVD-2025-34685) and CERT Bund (WID-SEC-2026-0057). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

• NetApp ActiveIQ Unified Manager

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Name

• Netty

License

• open-source

Website

• Product: https://github.com/netty/netty/

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