How severe is CVE-2026-5588?

No CVSS score has been assigned to CVE-2026-5588 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-5588?

CVE-2026-5588 affects the following packages: org.bouncycastle:bcpkix-jdk18on (Maven), org.bouncycastle:bcpkix-jdk15to18 (Maven), org.bouncycastle:bcpkix-jdk15on (Maven), org.bouncycastle:bcpkix-jdk14 (Maven), org.bouncycastle:bcpkix-debug-jdk18on (Maven), org.bouncycastle:bcpkix-debug-jdk15to18 (Maven), org.bouncycastle:bcpkix-debug-jdk14 (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-5588?

Update org.bouncycastle:bcpkix-jdk18on to 1.84 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-5588 is resolved across your whole dependency graph.

How do I detect CVE-2026-5588 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.bouncycastle:bcpkix-jdk18on, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-5588 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-5588 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-5588 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-5588?

CVE-2026-5588 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 56th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-5588?

CVE-2026-5588 is classified as Broken Cryptographic Algorithm (CWE-327), CWE-347 (CWE-347). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-5588 published, and has it been updated?

CVE-2026-5588 was published on April 15, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2026-5588 — bcpkix-jdk18on

Fix: bcgit/bc-java@656bae0

CVE-2026-5588 is a Broken Cryptographic Algorithm vulnerability in org.bouncycastle:bcpkix-jdk18on. A fix is available for org.bouncycastle:bcpkix-jdk18on — see the affected versions and patch details below.

PKIX draft CompositeVerifier accepts empty signature sequence as valid.

Also known asGHSA-wg6q-6289-32hp

Published

Apr 15, 2026

Updated

Oct 28, 2026

Affected

7 pkgs

Patched

7 / 7

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-5588.

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs56th percentile — riskier than 56% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

7 pkgs affected

☕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

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

7 total 7 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.bouncycastle:bcpkix-jdk18on`	≥ 1.49&&< 1.84	1.84`org.bouncycastle:bcpkix-jdk18on:1.84`
☕Maven	`org.bouncycastle:bcpkix-jdk15to18`	≥ 1.49&&< 1.84	1.84`org.bouncycastle:bcpkix-jdk15to18:1.84`
☕Maven	`org.bouncycastle:bcpkix-jdk15on`	≥ 1.49&&< 1.84	1.84`org.bouncycastle:bcpkix-jdk15on:1.84`
☕Maven	`org.bouncycastle:bcpkix-jdk14`	≥ 1.49&&< 1.84	1.84`org.bouncycastle:bcpkix-jdk14:1.84`
☕Maven	`org.bouncycastle:bcpkix-debug-jdk18on`	≥ 1.49&&< 1.84	1.84`org.bouncycastle:bcpkix-debug-jdk18on:1.84`
☕Maven	`org.bouncycastle:bcpkix-debug-jdk15to18`	≥ 1.49&&< 1.84	1.84`org.bouncycastle:bcpkix-debug-jdk15to18:1.84`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.bouncycastle:bcpkix-jdk18on, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.bouncycastle:bcpkix-jdk18on to 1.84 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-5588 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

To exploit this issue, an attacker needs to submit a crafted payload or token containing an empty signature sequence to an application using the `CompositeVerifier` for cryptographic validation. An attack typically requires the application to process this malformed data and improperly accept the empty sequence as a…

Workaround published by Red Hat

To mitigate this flaw, check that the signature sequence is not empty before passing any data to the CompositeVerifier for cryptographic validation. If the sequence is empty or null, explicitly reject the payload before it is processed.

Source: Red Hat security advisory for CVE-2026-5588 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat AMQ Broker 7.12.7	`bcpkix-jdk18on`	RHSA-2026:14276
Red Hat AMQ Broker 7.13.5	`bcpkix-jdk18on`	RHSA-2026:14272
Red Hat AMQ Broker 7.14.1	`bcpkix-jdk18on`	RHSA-2026:66488
Red Hat Build of Apache Camel 4.14 for Quarkus 3.27	`bcpkix-jdk18on`	RHSA-2026:13631
Red Hat build of Apache Camel 4.18.1 for Spring Boot 3.5.14	`bcpkix-jdk15on`	RHSA-2026:17668
Red Hat build of Quarkus 3.20.6.SP1	`org.bouncycastle/bcpkix-jdk18on:1.84.0.redhat-00001`	RHSA-2026:11720
Red Hat build of Quarkus 3.27.3.SP1	`org.bouncycastle/bcpkix-jdk18on:1.84.0.redhat-00001`	RHSA-2026:11721
Red Hat JBoss Enterprise Application Platform 7.4.25	`bcpkix-jdk18on`	RHSA-2026:53806

Frequently Asked Questions

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: fr

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