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Fencer Vulns
medium 6.5

CVE-2026-59638 json

JSSE hostname verifier CN-fallback enabled by default despite documented opt-in

published 2026-08-03 3 mo ago modified 2026-08-28 2 mo ago also EUVD-2026-52016

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

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 bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).

Patch / fix

  • Legion of the Bouncy Castle Inc. BC-JAVA 1.85
  • Legion of the Bouncy Castle Inc. BC-LTS-JAVA 2.73.12
  • Legion of the Bouncy Castle Inc. BC-FJA 1.0.24, 2.0.24, 2.1.24
  • bouncycastle Debian 14 1.86-1

debian advisories DEBIAN-CVE-2026-59638

  • bouncycastle SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 1.85-150200.3.38.1
  • bouncycastle SLES 16.0, SLES for SAP applications 16.0 1.85-160000.1.1

suse advisories SUSE-SU-2026:3559-1SUSE-SU-2026:23127-1SUSE-SU-2026:23150-1

  • bouncycastle openSUSE Leap 16.0 1.85-160000.1.1
  • bouncycastle openSUSE Tumbleweed 1.85-1.1

opensuse advisories openSUSE-SU-2026:21538-1openSUSE-SU-2026:11445-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-59638 updated cvss 7.4

org.bouncycastle/bctls-jdk15on: org.bouncycastle/bctls-fips: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier

  • Red Hat OpenShift Developer Tools and Services jenkins, jenkins-2-plugins, ocp-tools-4/jenkins-rhel9 Red Hat AMQ Broker 7 bcprov-jdk18on Red Hat AMQ Clients bcpg-jdk18on, bcprov-jdk15on, bcprov-jdk18on, bcutil-jdk18on Red Hat Ansible Automation Platform 2 ansible-automation-platform-27/de-minimal-rhel9 Red Hat build of Apache Camel 4 for Quarkus 3 bcpg-jdk18on, bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on, camel-quarkus-support-bouncycastle, camel-quarkus-support-bouncycastle-deployment Red Hat build of Apache Camel for Spring Boot 4 bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on, bouncycastle-project
    +15 more products
    Red Hat build of Apicurio Registry 3 bcprov-lts8on, bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on Red Hat Build of Keycloak rhbk/keycloak-rhel9 Red Hat build of Quarkus bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on Red Hat Ceph Storage 9 libarrow, parquet-libs Red Hat Enterprise Linux 8 resteasy, resteasy-javadoc Red Hat Enterprise Linux 9 jmc, resteasy, pki-resteasy-core, pki-resteasy-client, pki-resteasy-jackson2-provider, pki-resteasy-servlet-initializer Red Hat Fuse 7 bcpkix-jdk15on, bcprov-jdk15on, bcprov-jdk18on Red Hat JBoss Enterprise Application Platform 7 bcpg-jdk18on, bcmail-jdk18on, bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on Red Hat JBoss Enterprise Application Platform 8 bcpg-jdk18on, bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on, bcjmail-jdk18on Red Hat JBoss Enterprise Application Platform Expansion Pack bcpg-jdk18on, bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on, bcjmail-jdk18on Red Hat OpenShift AI (RHOAI) rhoai/odh-modelmesh-rhel9, rhoai/odh-spark-operator-rhel9 Red Hat OpenShift Dev Spaces devspaces/openvsx-rhel9 Red Hat OpenStack Platform 13 (Queens) opendaylight Red Hat Satellite 6 candlepin, candlepin-selinux Red Hat Single Sign-On 7 bcpg-jdk18on, bcmail-jdk18on, bcpkix-jdk18on, bcprov-jdk18on, bcutil-jdk18on
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
total
Assessed
3 mo ago

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 9.3 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
CNA 4.0 9.3 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected products

  • Legion of the Bouncy Castle Inc. BC-JAVA
  • Legion of the Bouncy Castle Inc. BC-LTS-JAVA
  • Legion of the Bouncy Castle Inc. BC-FJA

Classification

Weakness
  • CWE-297 Improper Validation of Certificate with Host Mismatch

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.