XML External Entity injection in Netty - CVE-2026-56817

Vulnerability identifier: #VU137565

CSH Severity: Medium

CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-56817

CWE-ID: CWE-611

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to inject XML entities.

The vulnerability exists due to improper configuration in XmlDecoder when parsing XML containing a DOCTYPE declaration. A remote attacker can send specially crafted XML data to inject XML entities.

Whether external entities are actually resolved depends on Aalto XML's asynchronous parser behavior, making exploitability conditional.

Netty
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
Development Tools Module
SUSE Package Hub 15
netty-tcnative-debugsource
netty-tcnative
netty
netty-javadoc

Install security update from vendor's website.

Netty - addressed in versions 4.1.136, 4.2.16
netty-tcnative-debugsource - update to 2.0.80-150200.3.48.1
netty-tcnative - update to 2.0.80-150200.3.48.1
netty - update to 4.1.136-150200.4.53.1
netty-javadoc - update to 4.1.136-150200.4.53.1

• https://github.com/netty/netty/security/advisories/GHSA-4qhr-g3c6-fcfx

• Multiple vulnerabilities in Netty
• SUSE update for netty, netty-tcnative