CVE-2026-93563

CVE-2026-93563

High · published September 18, 2026

CVSS v3.1
7.5
EPSS
0%
Percentile
24.3
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00325 · 24.3th percentile
Published
2026-09-18T15:17Z
References (2)
https://access.redhat.com/security/cve/CVE-2026-93563 · [email protected]https://bugzilla.redhat.com/show_bug.cgi?id=2536976 · [email protected]
EPSS history
Timeline
  • 20 SEP 03:25Z
    EPSS moved — → 0%
    epss
  • 18 SEP 10:58Z
    Netty: netty-codec-smtp: io.netty/netty-codec-smtp: netty: unbounded multi-line response accumulation in smtpresponsedecoder leads to memory-exhaustion dos
    cvelistv5