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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat build of Apache Camel for Spring Boot 4 | — | — |
| Red Hat | Red Hat Fuse 7 | — | — |
| Red Hat | Red Hat JBoss Enterprise Application Platform 7 | — | — |
| Red Hat | Red Hat Single Sign-On 7 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | netty | No fix yet | — |
| Debian 13 | netty | No fix yet | — |
| Debian 12 | netty | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | netty | No fix yet | — |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 26.04 LTS | netty | No fix yet | — |
| Ubuntu Pro 24.04 LTS | netty | No fix yet | — |
| Ubuntu Pro 22.04 LTS | netty | No fix yet | — |
| Ubuntu Pro 20.04 LTS | netty | No fix yet | — |
| Ubuntu Pro 18.04 LTS | netty | No fix yet | — |
| Ubuntu Pro 16.04 LTS | netty | No fix yet | — |
| Ubuntu Pro 14.04 LTS | netty | No fix yet | — |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | netty | 4.1.138-150200.4.56.1 | SUSE-SU-2026:4391-1 |
| SLES 15 SP7 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
| SLES 15 SP6 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
| SLES 15 SP5 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
| SLES 15 SP4 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP6 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
| SLES for SAP 15 SP5 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
| SLES for SAP 15 SP4 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
| SLE HPC 15 SP5 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
| SLE HPC 15 SP4 | netty-tcnative | 2.0.84-150200.3.51.1 | SUSE-SU-2026:4391-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | netty | 4.1.138-1.1 | openSUSE-SU-2026:11882-1 |
Advisories 3
- WID-SEC-2026-3477 Netty: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 8, 2026
- SUSE-SU-2026:4391-1 Security update for netty, netty-tcnative SUSE / openSUSE Security Updates · Sep 30, 2026
- openSUSE-SU-2026:11882-1 netty-4.1.138-1.1 on GA media SUSE / openSUSE Security Updates · Sep 25, 2026
References
- https://access.redhat.com/security/cve/CVE-2026-93563 vdb-entry
- RHBZ#2536976 issue-tracking