CVE-2026-5588: PKIX draft CompositeVerifier accepts empty signature sequence as valid.

Published Apr 15, 2026
·
Updated

: 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.

Other sources

Use of a Broken or Risky Cryptographic Algorithm vulnerability in Legion of the Bouncy Castle Inc. BC-JAVA bcpkix on all (pkix modules), Legion of the Bouncy Castle Inc. BCPKIX-FIPS bcpkix on All (pkix modules), Legion of the Bouncy Castle Inc. BCPIX-LTS bcpkix on All (pkix modules).

This vulnerability is associated with program files JcaContentVerifierProviderBuilder.Java, JcaContentVerfierProviderBuilder.Java.

This issue affects BC-JAVA: from 1.67 before 1.80.2, from 1.81 before 1.81.1, from 1.82 before 1.84; BCPKIX-FIPS: from 2.0.6 before 2.0.11, from 2.1.7 before 2.1.11; BCPIX-LTS: from 2.73.7 before 2.73.11.

— MITRE

Affected Software

10 affected componentsFixes available
Bouncy Castle BC-JAVA bcpkix>=1.49<1.84
maven/org.bouncycastle:bcpkix-debug-jdk14>=1.49<1.84
1.84
maven/org.bouncycastle:bcpkix-debug-jdk15to18>=1.49<1.84
1.84
maven/org.bouncycastle:bcpkix-debug-jdk18on>=1.49<1.84
1.84
maven/org.bouncycastle:bcpkix-jdk14>=1.49<1.84
1.84
maven/org.bouncycastle:bcpkix-jdk15on>=1.49<1.84
1.84
maven/org.bouncycastle:bcpkix-jdk15to18>=1.49<1.84
1.84
maven/org.bouncycastle:bcpkix-jdk18on>=1.49<1.84
1.84
IBM MQ Operator<=SC2: v3.2.0 - v3.2.23 CD:  v3.3.0, v3.4.0, v3.4.1, v3.5.0, v3.5.1 - v3.5.3, v3.6.0 - v3.6.4, v3.7.0 - v3.7.2, v3.8.0, v3.8.1, v3.9.0, v3.9.1 LTS: v2.0.0 - 2.0.29
IBM supplied MQ Advanced container images<=SC2: 9.4.0.6-r1, 9.4.0.6-r2, 9.4.0.7-r1, 9.4.0.10-r1, 9.4.0.10-r2, 9.4.0.11-r1, 9.4.0.11-r2, 9.4.0.11-r3, 9.4.0.12-r1, 9.4.0.15-r1 - 9.4.0.15-r4, 9.4.0.16-r1, 9.4.0.16-r2, 9.4.0.17-r1, 9.4.0.17-r2, 9.4.0.20-r1CD: 9.4.1.0-r1, 9.4.1.0-r2, 9.4.1.1-r1, 9.4.2.0-r1, 9.4.2.0-r2, 9.4.2.1-r1, 9.4.2.1-r2, 9.4.3.0-r1, 9.4.3.0-r2, 9.4.3.1-r1 - 9.4.3.1-r3, 9.4.4.0-r1 - 9.4.4.0-r4, 9.4.4.1-r1, 9.4.5.0-r1, 9.4.5.0-r2LTS: 9.3.0.0-r1, 9.3.0.0-r2, 9.3.0.0-r3, 9.3.0.1-r1, 9.3.0.1-r2, 9.3.0.1-r3, 9.3.0.1-r4, 9.3.0.3-r1, 9.3.0.4-r1, 9.3.0.4-r2, 9.3.0.5-r1, 9.3.0.5-r2, 9.3.0.5-r3, 9.3.0.6-r1, 9.3.0.10-r1, 9.3.0.10-r2, 9.3.0.11-r1,9.3.0.11-r2, 9.3.0.15-r1, 9.3.0.16-r1, 9.3.0.16-r2, 9.3.0.17-r1, 9.3.0.17-r2, 9.3.0.17-r3, 9.3.0.20-r1, 9.3.0.20-r2, 9.3.0.21-r1, 9.3.0.21-r2, 9.3.0.21-r3, 9.3.0.25-r1, 9.4.0.0-r1, 9.4.0.0-r2, 9.4.0.0-r3, 9.4.0.5-r1, 9.4.0.5-r2

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade maven/org.bouncycastle:bcpkix-debug-jdk14 to a version that resolves this vulnerability.

    Fixed in 1.84
  2. Upgrade

    Upgrade maven/org.bouncycastle:bcpkix-debug-jdk15to18 to a version that resolves this vulnerability.

    Fixed in 1.84
  3. Upgrade

    Upgrade maven/org.bouncycastle:bcpkix-debug-jdk18on to a version that resolves this vulnerability.

    Fixed in 1.84
  4. Upgrade

    Upgrade maven/org.bouncycastle:bcpkix-jdk14 to a version that resolves this vulnerability.

    Fixed in 1.84
  5. Upgrade

    Upgrade maven/org.bouncycastle:bcpkix-jdk15on to a version that resolves this vulnerability.

    Fixed in 1.84
  6. Upgrade

    Upgrade maven/org.bouncycastle:bcpkix-jdk15to18 to a version that resolves this vulnerability.

    Fixed in 1.84
  7. Upgrade

    Upgrade maven/org.bouncycastle:bcpkix-jdk18on to a version that resolves this vulnerability.

    Fixed in 1.84

Event History

Apr 15, 2026
CVE Published
via MITRE·09:06 AM
Data Sourced
via MITRE·09:06 AM
DescriptionWeakness
Data Sourced
via Red Hat·10:01 AM
DescriptionSeverityAffected Software
Data Sourced
via NVD·10:16 AM
DescriptionSeverityWeakness
Advisory Published
via GitHub·06:31 PM
Data Sourced
via GitHub·06:31 PM
DescriptionWeaknessAffected Software
May 15, 2026
Data Sourced
via IBM·12:00 AM
DescriptionAffected Software

Parent advisories

This vulnerability appears in the following advisories.

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Frequently Asked Questions

1

What is the severity of CVE-2026-5588?

CVE-2026-5588 is considered a moderate severity vulnerability due to its potential impact on cryptographic integrity.

2

How do I fix CVE-2026-5588?

To fix CVE-2026-5588, update the Bouncy Castle BC-JAVA bcpkix library to version 1.84 or later.

3

What impact does CVE-2026-5588 have on my application?

CVE-2026-5588 allows the acceptance of empty signature sequences, which may lead to verification of invalid signatures.

4

Is CVE-2026-5588 related to any specific software versions?

Yes, CVE-2026-5588 affects all versions of Bouncy Castle BC-JAVA bcpkix between 1.49 and 1.84.

5

Who is affected by CVE-2026-5588?

Any application using the affected versions of Bouncy Castle BC-JAVA bcpkix library is vulnerable to CVE-2026-5588.

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