CVE-2025-59419: 
Java vulnerability analysis and mitigation

CVE-2025-59419 affects Netty, an asynchronous event-driven network application framework, specifically its SMTP codec in versions prior to 4.1.128.Final and 4.2.7.Final. The vulnerability is an SMTP command injection flaw that exists due to insufficient input validation for Carriage Return (\r) and Line Feed (\n) characters in user-supplied parameters. The issue was discovered and disclosed on October 15, 2025 (GitHub Advisory).

The vulnerability exists in io.netty.handler.codec.smtp.DefaultSmtpRequest, where parameters are directly concatenated into the SMTP command string without proper sanitization. When methods such as SmtpRequests.rcpt(recipient) are called with a malicious string containing CRLF sequences, attackers can inject arbitrary SMTP commands. The vulnerability has been assigned a CVSS 4.0 score of 5.5 (Medium) with the vector string CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P. The weakness is classified as CWE-93 (Improper Neutralization of CRLF Sequences) (NVD).

The vulnerability allows remote attackers who can control SMTP command parameters to forge arbitrary emails from trusted servers. Since 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 can be exploited for economic manipulation, disinformation campaigns, and sophisticated phishing attacks by impersonating executives and forging high-stakes corporate communications (GitHub Advisory).

The vulnerability has been patched in versions 4.1.129.Final and 4.2.8.Final. No known workarounds exist, making it critical for affected users to upgrade to the patched versions (NVD).