CVE-2026-5588: Bouncy Castle Use Of A Broken Or Vulnerability

MODERATE
Advisory Identifier: GHSA-wg6q-6289-32hp
Share
CWE-327
Published
Advisory Summary

CVE-2026-5588 is a MODERATE use of a broken or vulnerability (CWE-327: Use of a Broken or Risky Cryptographic Algorithm) affecting Bouncy Castle libraries in the Maven ecosystem. The issue involves use of a broken or risky cryptographic algorithm vulnerability in bcpkix modules. Remediation is available by upgrading affected packages to version 1.84.

CVE-2026-5588 at a Glance

CVE Identifier CVE-2026-5588
GHSA Identifier GHSA-wg6q-6289-32hp
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-327: Use of a Broken or Risky Cryptographic Algorithm
Affected Product Bouncy Castle
Package Ecosystem Maven
Published Date
Last Updated

How to Fix CVE-2026-5588

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:bcpkix-jdk18on fixed: 1.84 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk18on</artifactId>
    <version>1.84</version>
</dependency>
org.bouncycastle:bcpkix-jdk15to18 fixed: 1.84 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk15to18</artifactId>
    <version>1.84</version>
</dependency>
org.bouncycastle:bcpkix-jdk15on fixed: 1.84 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk15on</artifactId>
    <version>1.84</version>
</dependency>
org.bouncycastle:bcpkix-jdk14 fixed: 1.84 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-jdk14</artifactId>
    <version>1.84</version>
</dependency>
org.bouncycastle:bcpkix-debug-jdk18on fixed: 1.84 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-debug-jdk18on</artifactId>
    <version>1.84</version>
</dependency>
org.bouncycastle:bcpkix-debug-jdk15to18 fixed: 1.84 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-debug-jdk15to18</artifactId>
    <version>1.84</version>
</dependency>
org.bouncycastle:bcpkix-debug-jdk14 fixed: 1.84 
<dependency>
    <groupId>org.bouncycastle</groupId>
    <artifactId>bcpkix-debug-jdk14</artifactId>
    <version>1.84</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-2026-5588, 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 1.84), 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 & Technical Analysis

This vulnerability is classified under CWE-327: Use of a Broken or Risky Cryptographic Algorithm, where the product uses a broken or risky cryptographic algorithm or protocol. In Bouncy Castle, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

: Use of a Broken or Risky Cryptographic Algorithm vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA bcpkix on all (pkix modules). PKIX draft CompositeVerifier accepts empty signature sequence as valid. This issue affects BC-JAVA: from 1.49 before 1.84.

CVE-2026-5588 Affected Bouncy Castle Versions

7 component(s)
Fixed Versions:
1.84
Product / Package Ecosystem Affected Versions Fixed Version
org.bouncycastle:bcpkix-jdk18on
maven/org.bouncycastle/bcpkix-jdk18on
Maven
≥ 1.49
< 1.84
1.84
org.bouncycastle:bcpkix-jdk15to18
maven/org.bouncycastle/bcpkix-jdk15to18
Maven
≥ 1.49
< 1.84
1.84
org.bouncycastle:bcpkix-jdk15on
maven/org.bouncycastle/bcpkix-jdk15on
Maven
≥ 1.49
< 1.84
1.84
org.bouncycastle:bcpkix-jdk14
maven/org.bouncycastle/bcpkix-jdk14
Maven
≥ 1.49
< 1.84
1.84
org.bouncycastle:bcpkix-debug-jdk18on
maven/org.bouncycastle/bcpkix-debug-jdk18on
Maven
≥ 1.49
< 1.84
1.84
org.bouncycastle:bcpkix-debug-jdk15to18
maven/org.bouncycastle/bcpkix-debug-jdk15to18
Maven
≥ 1.49
< 1.84
1.84
org.bouncycastle:bcpkix-debug-jdk14
maven/org.bouncycastle/bcpkix-debug-jdk14
Maven
≥ 1.49
< 1.84
1.84

References

NVD — CVE-2026-5588 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-5588
Security Fix Commit FIX COMMIT
https://github.com/bcgit/bc-java/commit/656bae0dbd9b1521f840521ff786e78749fe3057
Bouncy Castle Source Repository REPOSITORY
https://github.com/bcgit/bc-java
GitHub Advisory / Wiki ADVISORY
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%905588

Frequently Asked Questions

What is CVE-2026-5588?
CVE-2026-5588 is a security vulnerability in Bouncy Castle involving Use of a Broken or Risky Cryptographic Algorithm vulnerability in bcpkix modules under CWE-327: Use of a Broken or Risky Cryptographic Algorithm.
Which Bouncy Castle versions are affected?
Affected versions include releases prior to 1.84 across affected packages: org.bouncycastle:bcpkix-jdk18on, org.bouncycastle:bcpkix-jdk15to18, org.bouncycastle:bcpkix-jdk15on, org.bouncycastle:bcpkix-jdk14, org.bouncycastle:bcpkix-debug-jdk18on, org.bouncycastle:bcpkix-debug-jdk15to18, org.bouncycastle:bcpkix-debug-jdk14.
What version fixes CVE-2026-5588?
Upgrading to 1.84 (or the latest patched release for your respective branch) resolves the vulnerability.
Is bcpkix-jdk18on affected?
Yes, org.bouncycastle:bcpkix-jdk18on is affected in releases prior to 1.84. Upgrade your dependency to 1.84 or later.
Is bcpkix-jdk15to18 affected?
Yes, org.bouncycastle:bcpkix-jdk15to18 is affected in releases prior to 1.84. Upgrade your dependency to 1.84 or later.
What CWE is associated with CVE-2026-5588?
CVE-2026-5588 is classified under CWE-327: Use of a Broken or Risky Cryptographic Algorithm (The product uses a broken or risky cryptographic algorithm or protocol.).
How can I check Maven dependencies for CVE-2026-5588?
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-wg6q-6289-32hp",
  "modified" : "2026-04-16T21:32:20Z",
  "published" : "2026-04-15T18:31:54Z",
  "aliases" : [ "CVE-2026-5588" ],
  "summary" : "Bouncy Castle Crypto Package For Java: Use of a Broken or Risky Cryptographic Algorithm vulnerability in bcpkix modules",
  "details" : ": Use of a Broken or Risky Cryptographic Algorithm vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA bcpkix on all (pkix modules).\n\n\nPKIX draft CompositeVerifier accepts empty signature sequence as valid.\n\n\nThis issue affects BC-JAVA: from 1.49 before 1.84.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/U:Green"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcpkix-jdk18on"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.49"
      }, {
        "fixed" : "1.84"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcpkix-jdk15to18"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.49"
      }, {
        "fixed" : "1.84"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcpkix-jdk15on"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.49"
      }, {
        "fixed" : "1.84"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcpkix-jdk14"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.49"
      }, {
        "fixed" : "1.84"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcpkix-debug-jdk18on"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.49"
      }, {
        "fixed" : "1.84"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcpkix-debug-jdk15to18"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.49"
      }, {
        "fixed" : "1.84"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bouncycastle:bcpkix-debug-jdk14"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.49"
      }, {
        "fixed" : "1.84"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-5588"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-java/commit/656bae0dbd9b1521f840521ff786e78749fe3057"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/bcgit/bc-java"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%905588"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-327" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-16T21:32:20Z",
    "nvd_published_at" : "2026-04-15T10:16:49Z"
  }
}