AIKIDO-2026-645787
netty-codec-smtp is vulnerable to Denial of Service (DoS)
75
High Risk
This Affects:
netty-codec-smtpTL;DR
SmtpResponseDecoder accumulates SMTP multi-line response continuation lines into an uncapped list. A malicious or MITM SMTP server that withholds the space-separated terminator line and streams unbounded 250-x continuation lines drives the list to grow without bound across decode calls, exhausting the JVM heap. This results in a denial of service for the SMTP client. The fix bounds the accumulated continuation lines.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and your application uses the SMTP client codec against untrusted or MITM-capable SMTP servers.
Background info
netty-codec-smtp is vulnerable to Denial of Service (DoS) in versions 4.1.0.Final - 4.1.137.Final and 4.2.0.Final - 4.2.17.Final.
How to fix this
Upgrade the io.netty:netty-codec-smtp library to the patch version.
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