CVE-2026-93563

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 v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://access.redhat.com/security/cve/CVE-2026-93563
https://bugzilla.redhat.com/show_bug.cgi?id=2536976

Configurations

No configuration.

History

18 Sep 2026, 21:18

Type	Values Removed	Values Added
Summary	~~(en) Unbounded multi-line response accumulation in SmtpResponseDecoder leads to memory-exhaustion DoS~~	(en) 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.

18 Sep 2026, 14:19

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5

18 Sep 2026, 11:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-09-18 11:17

Updated : 2026-09-25 09:17

NVD link : CVE-2026-93563

Mitre link : CVE-2026-93563

CVE.ORG link : CVE-2026-93563

JSON object : View

Products Affected

No product.

CWE

CWE-1035

OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities

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