CRLF Injection Affecting netty package, versions <1:4.1.48-9ubuntu0.1~esm2


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.3% (53rd percentile)

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  • Snyk IDSNYK-UBUNTU2404-NETTY-15742405
  • published21 Mar 2026
  • disclosed15 Oct 2025

Introduced: 15 Oct 2025

CVE-2025-59419  (opens in a new tab)
CWE-93  (opens in a new tab)

How to fix?

Upgrade Ubuntu:24.04 netty to version 1:4.1.48-9ubuntu0.1~esm2 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream netty package and not the netty package as distributed by Ubuntu. See How to fix? for Ubuntu:24.04 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1