CVE-2026-8763: Bouncy Castle Name Constraints Bypass Vulnerability

CRITICAL
Advisory Identifier: GHSA-9pwp-9qqc-pr26
Share
CVSS 9.1
CWE-295
Published
Advisory Summary

CVE-2026-8763 is a CRITICAL (CVSS 9.1) name constraints bypass vulnerability (CWE-295: Improper Certificate Validation) affecting Bouncy Castle libraries in the Maven ecosystem. The issue involves name constraints bypass via trailing dot in rfc822name and uri. Remediation is available by upgrading affected packages to version 1.0.2.7, 2.0.2, 2.1.3, 1.85, 2.73.12.

CVE-2026-8763 at a Glance

CVE Identifier CVE-2026-8763
GHSA Identifier GHSA-9pwp-9qqc-pr26
Severity CRITICAL
CVSS v3.1 Base Score 9.1
CWE Classification CWE-295: Improper Certificate Validation
Affected Product Bouncy Castle
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-8763

To remediate this vulnerability, upgrade all affected Bouncy Castle dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.bouncycastle:bc-fips fixed: 1.0.2.7 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bc-fips</artifactId>
    <version>1.0.2.7</version>
</dependency>
org.bouncycastle:bc-fips fixed: 2.0.2 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bc-fips</artifactId>
    <version>2.0.2</version>
</dependency>
org.bouncycastle:bc-fips fixed: 2.1.3 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bc-fips</artifactId>
    <version>2.1.3</version>
</dependency>
org.bouncycastle:bcprov-jdk18on fixed: 1.85 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-jdk18on</artifactId>
    <version>1.85</version>
</dependency>
org.bouncycastle:bcprov-lts8on fixed: 2.73.12 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-lts8on</artifactId>
    <version>2.73.12</version>
</dependency>
org.bouncycastle:bcprov-jdk15to18 fixed: 1.85 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcprov-jdk15to18</artifactId>
    <version>1.85</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.bouncycastle

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-8763, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.bouncycastle

Analyze the terminal output to locate any version of Bouncy Castle in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.0.2.7), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.bouncycastle command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & RFC 5280 Specification

Under RFC 5280 specifications for X.509 certificates, the Name Constraints extension defines a namespace within which all subsequent subject names in a certification path must be located. Constraints apply to various name forms including directory names, IP addresses, rfc822Name (email addresses), and uniformResourceIdentifier (URI) entries. Specifically, during certificate path validation, affected versions of Bouncy Castle failed to properly normalize or enforce boundary checks when domain names contained trailing dot (.) characters. Because domain names with a trailing dot signify fully qualified domain names (FQDNs), this omission allowed non-conforming certificates to be improperly validated as compliant with the defined name constraints.

Source Advisory Statement

In Bouncy Castle for Java before 1.85, Name Constraints bypass via trailing dot in rfc822Name and URI. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 1.0.2.7 (1.0.X series), 2.0.2 (2.0.X series) and 2.1.3 (2.1.X series).

CVE-2026-8763 Affected Bouncy Castle Versions

6 component(s)
Fixed Versions:
1.0.2.72.0.22.1.31.852.73.12
Product / Package Ecosystem Affected Versions Fixed Version
org.bouncycastle:bc-fips
maven/org.bouncycastle/bc-fips
Maven
< 1.0.2.7
1.0.2.7
org.bouncycastle:bc-fips
maven/org.bouncycastle/bc-fips
Maven
≥ 2.0.0
< 2.0.2
2.0.2
org.bouncycastle:bc-fips
maven/org.bouncycastle/bc-fips
Maven
≥ 2.1.0
< 2.1.3
2.1.3
org.bouncycastle:bcprov-jdk18on
maven/org.bouncycastle/bcprov-jdk18on
Maven
< 1.85
1.85
org.bouncycastle:bcprov-lts8on
maven/org.bouncycastle/bcprov-lts8on
Maven
< 2.73.12
2.73.12
org.bouncycastle:bcprov-jdk15to18
maven/org.bouncycastle/bcprov-jdk15to18
Maven
< 1.85
1.85

References

NVD — CVE-2026-8763 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-8763
Security Fix Commit FIX COMMIT
https://github.com/bcgit/bc-java/commit/2c28b253a44681fbbc562561eab6ad383d2ae558
Bouncy Castle Source Repository REPOSITORY
https://github.com/bcgit/bc-java
Bouncy Castle Release RELEASE
https://github.com/bcgit/bc-java/releases/tag/r1rv85v2
GitHub Advisory / Wiki ADVISORY
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%908763
GitHub Advisory / Wiki ADVISORY
https://github.com/bcgit/bc-java/wiki/CVE-2026-8763

Frequently Asked Questions

What is CVE-2026-8763?
CVE-2026-8763 is a security vulnerability in Bouncy Castle involving Name Constraints bypass via trailing dot in rfc822Name and URI under CWE-295: Improper Certificate Validation.
Which Bouncy Castle versions are affected?
Affected versions include releases prior to 1.0.2.7, 2.0.2, 2.1.3, 1.85, 2.73.12 across affected packages: org.bouncycastle:bc-fips, org.bouncycastle:bcprov-jdk18on, org.bouncycastle:bcprov-lts8on, org.bouncycastle:bcprov-jdk15to18.
What version fixes CVE-2026-8763?
Upgrading to 1.0.2.7, 2.0.2, 2.1.3, 1.85, 2.73.12 (or the latest patched release for your respective branch) resolves the vulnerability.
Is bc-fips affected?
Yes, org.bouncycastle:bc-fips is affected in releases prior to 1.0.2.7, 2.0.2, 2.1.3. Upgrade your dependency to 1.0.2.7, 2.0.2, 2.1.3 or later.
Is bcprov-jdk18on affected?
Yes, org.bouncycastle:bcprov-jdk18on is affected in releases prior to 1.85. Upgrade your dependency to 1.85 or later.
What is the CVSS score of CVE-2026-8763?
CVE-2026-8763 has a CVSS v3.1 base score of 9.1 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-8763?
CVE-2026-8763 is classified under CWE-295: Improper Certificate Validation (The product does not validate, or incorrectly validates, a certificate.).
How can I check Maven dependencies for CVE-2026-8763?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.bouncycastle'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9pwp-9qqc-pr26",
  "modified" : "2026-09-18T17:36:32Z",
  "published" : "2026-08-03T03:31:56Z",
  "aliases" : [ "CVE-2026-8763" ],
  "summary" : "Bouncy Castle: Name Constraints bypass via trailing dot in rfc822Name and URI",
  "details" : "In Bouncy Castle for Java before 1.85, Name Constraints bypass via trailing dot in rfc822Name and URI. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 1.0.2.7 (1.0.X series), 2.0.2 (2.0.X series) and 2.1.3 (2.1.X series).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bc-fips"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.0.2.7"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bc-fips"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0"
      }, {
        "fixed" : "2.0.2"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bc-fips"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.1.0"
      }, {
        "fixed" : "2.1.3"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcprov-jdk18on"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.85"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcprov-lts8on"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.73.12"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcprov-jdk15to18"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.85"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-8763"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-java/commit/2c28b253a44681fbbc562561eab6ad383d2ae558"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/bcgit/bc-java"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-java/releases/tag/r1rv85v2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%908763"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-java/wiki/CVE-2026-8763"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-295" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-18T17:35:38Z",
    "nvd_published_at" : "2026-08-03T01:16:45Z"
  }
}