Netty has SMTP Command Injection Vulnerability that Allows Email Forgery

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2025-59419: 1.55% estimated exploitation activity in the next 30 days; percentile 75.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary An SMTP Command Injection (CRLF Injection) vulnerability in Netty's SMTP codec allows a remote attacker who can control SMTP command parameters (e.g., an email recipient) to forge arbitrary emails from the trusted server. This bypasses standard email authentication and can be used to impersonate executives and forge high-stakes corporate communications. Details The root cause is the lack of input validation for Carriage Return (\r) and Line Feed (\n) characters in user-supplied parameters. The vulnerable code is in io.netty.handler.codec.smtp.DefaultSmtpRequest, where parameters are directly concatenated into the SMTP command string. For example, when SmtpRequests.rcpt(recipient) is called, a malicious recipient string containing CRLF sequences can inject a new, separate SMTP command. Because the injected commands are sent from the server's trusted IP, any resulting emails will likely pass SPF and DKIM checks, making them appear legitimate to the victim's email client. PoC A…

Published by the source

15 Oct 2025, 17:12 UTC

Last modified by the source

17 Oct 2025, 21:32 UTC

Source last checked

26 Oct 2026, 16:40 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jq43-27x9-3v86

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# Patch Next advisory brief: CVE-2025-59419

Advisory: Netty has SMTP Command Injection Vulnerability that Allows Email Forgery
IDs: CVE-2025-59419, GHSA-jq43-27x9-3v86
Record: https://patchnext.com/advisories/cve-2025-59419 (revision 1, source checked 26 Oct 2026, 16:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.netty:netty-codec-smtp 4.2.7.Final, 4.1.128.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-codec-smtp: affected >= 4.2.0.Alpha1, < 4.2.7.Final; < 4.1.128.Final; fixed in 4.2.7.Final, 4.1.128.Final

## Suggested inspection (read-only)
- Maven io.netty:netty-codec-smtp: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.netty:netty-codec-smtp.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-jq43-27x9-3v86 (GitHub-reviewed advisory GHSA-jq43-27x9-3v86 lists affected ranges: Maven io.netty:netty-codec-smtp >=4.2.0.Alpha1 =0 <4.1.128.Final)

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