CVE-2026-93563

Io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos

Published Sep 18, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
A flaw was found in Netty's `SmtpResponseDecoder` component. A remote attacker, acting as a malicious or man-in-the-middle (MITM) SMTP server, could exploit this by sending a specially crafted, unbounded multi-line SMTP response without a terminator. This vulnerability leads to unbounded memory accumulation within the client's Java Virtual Machine (JVM) heap, causing an `OutOfMemoryError` and a denial of service (DoS) due to a process crash.

Remediation

Vendor Workaround

See https://github.com/netty/netty/security/advisories/GHSA-pq4x-537v-r54q for fixed versions and remediation guidance.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Io.netty
Io.netty netty-codec-http
Redhat build Of Apache Camel For Spring Boot
Redhat quay 3
Redhat single Sign-on
Vendors & Products Io.netty
Io.netty netty-codec-http
Redhat build Of Apache Camel For Spring Boot
Redhat quay 3
Redhat single Sign-on
Type Values Removed Values Added
Description Unbounded multi-line response accumulation in SmtpResponseDecoder leads to memory-exhaustion DoS A flaw was found in Netty's `SmtpResponseDecoder` component. A remote attacker, acting as a malicious or man-in-the-middle (MITM) SMTP server, could exploit this by sending a specially crafted, unbounded multi-line SMTP response without a terminator. This vulnerability leads to unbounded memory accumulation within the client's Java Virtual Machine (JVM) heap, causing an `OutOfMemoryError` and a denial of service (DoS) due to a process crash.
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title Netty: netty-codec-smtp: io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos Io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
Description Unbounded multi-line response accumulation in SmtpResponseDecoder leads to memory-exhaustion DoS
Title Netty: netty-codec-smtp: io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos
First Time appeared Redhat
Redhat camel Spring Boot
Redhat jboss Enterprise Application Platform
Redhat jboss Fuse
Redhat red Hat Single Sign On
Weaknesses CWE-1035
CPEs cpe:/a:redhat:camel_spring_boot:4
cpe:/a:redhat:jboss_enterprise_application_platform:7
cpe:/a:redhat:jboss_fuse:7
cpe:/a:redhat:red_hat_single_sign_on:7
Vendors & Products Redhat
Redhat camel Spring Boot
Redhat jboss Enterprise Application Platform
Redhat jboss Fuse
Redhat red Hat Single Sign On
References