CVE-2026-59638

Medium

Description

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).

SeverityMedium

CVSS6.5

Exploit probability—

ProductBouncycastle Bctls-fips

PublishedAug 3, 2026

First seenAug 3, 2026

Weakness typeCWE-297CWE-297

How to fix

Update

bouncycastle bctls-fips1.0.24, 2.0.24, 2.1.24 or later
bouncycastle bc-java1.85 or later

Patches

Vendor advisories

github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059638

Affected products

Product	Affected versions	Fixed in
bouncycastle bctls-fips	1.0.0 ≤ v < 1.0.24, 2.0.19 ≤ v < 2.0.24, 2.1.20 ≤ v < 2.1.24	1.0.24, 2.0.24, 2.1.24
bouncycastle bc-java	v < 1.85	1.85
bouncycastle bouncy_castle_for_java_lts	v ≤ 2.73.11	—

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