What is CVE-2026-42027?

CVE-2026-42027 is a critical-severity vulnerability in Apache Opennlp, classified under Use of Externally-Controlled Input to Select Classes or Code (Unsafe Reflection). CVSS score: 9.8/10. Published 2026-05-04.

How severe is CVE-2026-42027?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Apache Opennlp

CVE-2026-42027

Arbitrary Class Instantiation via Model Manifest in Apache OpenNLP ExtensionLoader Versions Affected: before 2.5.9, before 3.0.0-M3 Description: The ExtensionLoader.instantiateExtension(Class, String) method loads a class by it…

EPSS: 0.006 (71.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

Apache Opennlp — versions 3.0.0
Apache Software Foundation Opennlp — versions 0, 3.0

Weakness classification (CWE)

CWE-470 — Use of Externally-Controlled Input to Select Classes or Code (Unsafe Reflection)

References

security@apache.org (vendor-advisory, Mailing List, Vendor Advisory)
af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2026-42027?: CVE-2026-42027 is a critical-severity vulnerability in Apache Opennlp, classified under Use of Externally-Controlled Input to Select Classes or Code (Unsafe Reflection). CVSS score: 9.8/10. Published 2026-05-04.
How severe is CVE-2026-42027?: Critical severity. CVSS v3 base score is 9.8 out of 10.