Vulnerability Intelligence Report
JSSE hostname verifier CN-fallback enabled by default despite documented opt-in
CVE-2026-59638
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).
No Active Exploit Signals
CVSS Base Score
9.3
CRITICAL
EPSS Probability:0.28%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
—
Authentication
—
Weaponization
—
SSVC Action
—
Weaknesses (CWE)
CWE-297 ↗CWE-297 Improper Validation of Certificate with Host Mismatch
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Legion of the Bouncy Castle Inc. | BC-JAVA | 1.61 < 1.85 (affected) |
| Legion of the Bouncy Castle Inc. | BC-LTS-JAVA | 2.73.0 < 2.73.12 (affected) |
| Legion of the Bouncy Castle Inc. | BC-FJA | 1.0.7 < 1.0.24 (affected), 2.0.0 < 2.0.24 (affected), 2.1.0 < 2.1.24 (affected) |
References & Technical Advisories
No reference links found.
Threat Intelligence Signals
EPSS Score
0.276%
GitHub Advisory
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Legion of the Bouncy Castle Inc. · Open Source · Australia |
| Reserved | 2026-07-06T06:58:29 |
| Published | 2026-08-03T00:57:31 |
| Last Updated | 2026-08-03T13:23:06 |
Community Chatter & Buzz