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VulnerabilityCVE-2026-56817Published 2026-07-21

CVE-2026-56817 — netty

high (derived)

As of 2026-07-22, CVE-2026-56817 is a High-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in netty, CVSS v4.0 8.3, EPSS 0.5% (42.8th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-56817 as of 2026-07-22; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

CVSS v4.0
8.3/10High (derived)
EPSS
0.5%Higher than 42.8% of scored CVEs
CISA KEV
NoNot in the KEV catalog
Tracked threats
0None linked yet
Priority
5.9/10Threadlinqs triage score
Published
Updated 2026-07-22
CVSS v4.0 8.3 (High, derived from score) · EPSS 0.5% (higher than 42.8% of all scored CVEs) · Priority 5.9/10 · Published 2026-07-21

Last updated:

What is CVE-2026-56817?

Netty is a network application framework for development of protocol servers and clients. In versions 4.2.0.Final through 4.2.15.Final and 4.1.0.Final through 4.1.135.Final, any caller that can deliver bytes to a Netty channel pipeline containing `XmlDecoder` can send XML with a `DOCTYPE` declaration to an `AsyncXMLInputFactory` instantiated with no security configuration, leaving DTD and entity handling active depending on Aalto XML async parser behavior and creating conditional XML external entity risk. This issue is fixed in versions 4.1.136.Final and 4.2.16.Final.

The record classifies CVE-2026-56817 under weakness class CWE-611. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 76 days ago.

Severity and exploitation probability

CVSS v4.0 base score
8.3 — High (derived from score)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N
EPSS (FIRST)
0.5% probability of exploitation in the next 30 days, higher than 42.8% of all scored CVEs
CISA KEV
Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority
5.9/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published
2026-07-21, last modified 2026-07-22

Is CVE-2026-56817 being exploited?

It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

Affected products and versions

How to fix CVE-2026-56817

No vendor patch reference has been recorded for CVE-2026-56817 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2026-56817

No threat campaign in the Threadlinqs corpus currently references CVE-2026-56817, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.

Vendor advisory and patch

Other references