CVE-2026-59638

What it is

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).

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-08-03 01:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-08-28 17:29 UTC Last updatedMost recent change to the record

Details

Published

2026-08-03 01:16 UTC

Last modified

2026-08-28 17:29 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-297

Record status

Analyzed

Affected

• Bouncycastle bc-java < 1.85
• Bouncycastle bctls-fips < 1.0.24
• Bouncycastle bctls-fips < 2.0.24
• Bouncycastle bctls-fips < 2.1.24
• Bouncycastle Bouncy Castle For Java Lts ≤ 2.73.11

Attack profile CVSS 4.0 · 9.3

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

None