Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The netty-codec-smtp package (io.netty:netty-codec-smtp) from 4.2.0.Alpha1 before 4.2.7.Final, and from earlier 4.1 releases before 4.1.128.Final, does not reject carriage return and line feed characters in SMTP command parameters such as recipients. A remote attacker who can control those parameters may inject additional SMTP commands and send forged emails from the server. Upgrade to 4.2.7.Final or 4.1.128.Final, or later.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 5.5 | Medium | 4.0 | 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 | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.016, the 75th percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:17 UTC First seen by agentprime
- 31 Oct 2026, 14:17 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-jq43-27x9-3v86
- OSV: GHSA-jq43-27x9-3v86
- github.com/netty/netty/security/advisories/GHSA-jq43-27x9-3v86
- nvd.nist.gov/vuln/detail/CVE-2025-59419
- github.com/netty/netty/commit/1782e8c2060a244c4d4e6f9d9112d5517ca05120
- github.com/netty/netty/commit/2b3fddd3339cde1601f622b9ce5e54c39f24c3f9
- gist.github.com/DepthFirstDisclosures/ddacca28cb94b48fa8ab998cef59ed8c
- github.com/netty/netty
- www.depthfirst.com/post/our-ai-agent-found-a-netty-zero-day-that-bypasses-email-authentication-the-story-of-cve-2025-59419