---
id: CVE-2026-59638
title: >-
  In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback
  enabled by default despite documented opt-in
summary: >-
  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 bc…
severity: high
cwe:
  - CWE-297
  - CWE-295
published: '2026-08-03'
updated: '2026-08-03'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-59638'
references:
  - url: >-
      https://github.com/bcgit/bc-java/commit/5ac55351cd1a8a7184d41c96a7ee87df0770240a
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: >-
      https://github.com/bcgit/bc-java/commit/799bd15320a6310a447863638aa3df64acef829b
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: 'https://github.com/bcgit/bc-java/wiki/CVE-2026-59638'
    label: 91579145-5d7b-4cc5-b925-a0262ff19630
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-59638.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-59638'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-59638'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-59638'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2510201'
tags:
  - nvd
  - csaf
  - vex
  - red-hat
ingestedAt: '2026-08-03T01:21:07.697Z'
epss: 0.00345
epssPercentile: 0.25285
vendor: Red Hat
cvss: 7.4
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N'
cvssSource: vendor
---

## Overview

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).

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Vendor advisories

- **Red Hat VEX** · updated 2026-09-14 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-59638.json)