CVE-2026-59638

EUVD-2026-52016
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).
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
6.5 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: 11.47%
Affected Products (NVD)
VendorProductVersion
bouncycastlebc-java
𝑥
< 1.85
bouncycastlebctls-fips
1.0.0 ≤
𝑥
< 1.0.24
bouncycastlebctls-fips
2.0.19 ≤
𝑥
< 2.0.24
bouncycastlebctls-fips
2.1.20 ≤
𝑥
< 2.1.24
bouncycastlebouncy_castle_for_java_lts
𝑥
≤ 2.73.11
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
bouncycastle
bookworm
vulnerable
forky
vulnerable
sid
vulnerable
trixie
vulnerable
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
bouncycastle
bionic
needs-triage
focal
needs-triage
jammy
needs-triage
noble
needs-triage
resolute
needs-triage
xenial
needs-triage
Amazon Linux logo
Amazon Linux Releases
Amazon Package
Release
bouncycastle
Amazon Linux 2023
0:1.70-4.amzn2023.0.8
fixed
bouncycastle-javadoc
Amazon Linux 2023
0:1.70-4.amzn2023.0.8
fixed
bouncycastle-mail
Amazon Linux 2023
0:1.70-4.amzn2023.0.8
fixed
bouncycastle-pg
Amazon Linux 2023
0:1.70-4.amzn2023.0.8
fixed
bouncycastle-pkix
Amazon Linux 2023
0:1.70-4.amzn2023.0.8
fixed
bouncycastle-tls
Amazon Linux 2023
0:1.70-4.amzn2023.0.8
fixed
bouncycastle-util
Amazon Linux 2023
0:1.70-4.amzn2023.0.8
fixed
Common Weakness Enumeration
References
https://github.com/bcgit/bc-java/commit/5ac55351cd1a8a7184d41c96a7ee87df0770240a
https://github.com/bcgit/bc-java/commit/799bd15320a6310a447863638aa3df64acef829b
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059638