CVE-2026-59638 CRITICAL

CVE-2026-59638: JSSE hostname verifier CN-fallback enabled by default despite documented opt-in

Vendor Legion Of The Bouncy Castle Inc.
Product BC-JAVA
Weakness CWE-297
Published August 3, 2026
Last update August 3, 2026
View on NVD All CVEs

CVSS base score

9.3/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber

What the vulnerability does

01Description

In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback enabled by default despite documented opt-in. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).

Key dates

02Disclosure timeline

August 3, 2026 CVE published
August 3, 2026 Record updated