High severity · published Sep 18, 2026
CVE-2026-93563
Io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos
7.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 25% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RH
Red Hat JBoss Enterprise Application Platform 7 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Single Sign-On 7 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat build of Apache Camel for Spring Boot 4 · Red Hat
All versions, or not specified · source: vendor
Affected product
RH
Red Hat build of Apache Camel for Spring Boot 4
Red Hat
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-93563
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-93563
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-93563
bugzilla.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2536976
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