CVE-2026-59638
published 2026-08-03CVE-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…
PriorityP336medium6.5CVSS 3.1
AVNACLPRNUINSUCLILAN
EPSS
0.34%
26.8th percentile
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).
Affected
10 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| bouncycastle | bc-java | < 1.85 | 1.85 |
| bouncycastle | bctls-fips | >= 1.0.0 < 1.0.24 | 1.0.24 |
| bouncycastle | bctls-fips | >= 2.0.19 < 2.0.24 | 2.0.24 |
| bouncycastle | bctls-fips | >= 2.1.20 < 2.1.24 | 2.1.24 |
| bouncycastle | bouncy_castle_for_java_lts | <= 2.73.11 | — |
| legion_of_the_bouncy_castle_inc | bc-fja | >= 1.0.7 < 1.0.24 | 1.0.24 |
| legion_of_the_bouncy_castle_inc | bc-fja | >= 2.0.0 < 2.0.24 | 2.0.24 |
| legion_of_the_bouncy_castle_inc | bc-fja | >= 2.1.0 < 2.1.24 | 2.1.24 |
| legion_of_the_bouncy_castle_inc | bc-java | >= 1.61 < 1.85 | 1.85 |
| legion_of_the_bouncy_castle_inc | bc-lts-java | >= 2.73.0 < 2.73.12 | 2.73.12 |
CVSS provenance
nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
nvdv4.09.3CRITICALCVSS: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
vendor_redhat6.5MEDIUM
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Red Hat
org.bouncycastle/bctls-jdk15on: org.bouncycastle/bctls-fips: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier
vendor_redhat·2026-08-03·CVSS 6.5
CVE-2026-59638 [MEDIUM] CWE-295 org.bouncycastle/bctls-jdk15on: org.bouncycastle/bctls-fips: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier
org.bouncycastle/bctls-jdk15on: org.bouncycastle/bctls-fips: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier
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).
A flaw was found in Bouncy Castle for Java. The Java Secure Socket Extension (JSSE) hostname verifier incorrectly enables the Common Name (CN) fallback by default, despite it being documented as an opt-in feature. This misconfiguration could allow a remote attacker to bypass proper hostname validation by presenting a spe
GHSA
In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback enabled by default despite documented opt-in.
ghsa_unreviewed·2026-08-03
CVE-2026-59638 [CRITICAL] CWE-297 In Bouncy Castle for Java before 1.85, JSSE hostname verifier CN-fallback enabled by default despite documented opt-in.
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).
VulDB
Legion of the Bouncy Castle Bouncy Castle for Java FIPS JSSE Hostname Verifier access control
vuldb·2026-08-03·CVSS 9.3
CVE-2026-59638 [CRITICAL] Legion of the Bouncy Castle Bouncy Castle for Java FIPS JSSE Hostname Verifier access control
A vulnerability categorized as critical has been discovered in Legion of the Bouncy Castle Bouncy Castle for Java FIPS, Bouncy Castle for Java LTS and Bouncy Castle for Java. Affected is an unknown function of the component JSSE Hostname Verifier. The manipulation results in improper access controls.
This vulnerability was named CVE-2026-59638. The attack may be performed from remote. There is no available exploit.
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-59638 bouncycastle: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier [fedora-all]
bugzilla·2026-09-14·CVSS 6.5
CVE-2026-59638 [MEDIUM] CVE-2026-59638 bouncycastle: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier [fedora-all]
CVE-2026-59638 bouncycastle: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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).
Bugzilla
CVE-2026-59638 bouncycastle: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier [epel-all]
bugzilla·2026-09-14·CVSS 6.5
CVE-2026-59638 [MEDIUM] CVE-2026-59638 bouncycastle: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier [epel-all]
CVE-2026-59638 bouncycastle: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier [epel-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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).
Bugzilla
CVE-2026-59638 org.bouncycastle/bctls-jdk15on: org.bouncycastle/bctls-fips: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier
bugzilla·2026-08-03·CVSS 6.5
CVE-2026-59638 [MEDIUM] CVE-2026-59638 org.bouncycastle/bctls-jdk15on: org.bouncycastle/bctls-fips: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier
CVE-2026-59638 org.bouncycastle/bctls-jdk15on: org.bouncycastle/bctls-fips: Bouncy Castle for Java: Improper hostname validation due to default CN-fallback in JSSE verifier
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).
2026-08-03
Published