CVE-2026-5588 — bcpkix-jdk18on
Fix: bcgit/bc-java@656bae0CVE-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.
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
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
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-jdk14Real-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
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.bouncycastle:bcpkix-jdk18on | ≥ 1.49&&< 1.84 | 1.84org.bouncycastle:bcpkix-jdk18on:1.84 |
| ☕Maven | org.bouncycastle:bcpkix-jdk15to18 | ≥ 1.49&&< 1.84 | 1.84org.bouncycastle:bcpkix-jdk15to18:1.84 |
| ☕Maven | org.bouncycastle:bcpkix-jdk15on | ≥ 1.49&&< 1.84 | 1.84org.bouncycastle:bcpkix-jdk15on:1.84 |
| ☕Maven | org.bouncycastle:bcpkix-jdk14 | ≥ 1.49&&< 1.84 | 1.84org.bouncycastle:bcpkix-jdk14:1.84 |
| ☕Maven | org.bouncycastle:bcpkix-debug-jdk18on | ≥ 1.49&&< 1.84 | 1.84org.bouncycastle:bcpkix-debug-jdk18on:1.84 |
| ☕Maven | org.bouncycastle:bcpkix-debug-jdk15to18 | ≥ 1.49&&< 1.84 | 1.84org.bouncycastle:bcpkix-debug-jdk15to18:1.84 |
Detection & mitigation playbook
Open-source dependencyDetect
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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-5588 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-5588. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
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…
| 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 | bcpkix-jdk18on | RHSA-2026:11720 |
| Red Hat build of Quarkus 3.27.3.SP1 | bcpkix-jdk18on | RHSA-2026:11721 |
| Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7 | eap7-activemq-artemis-0:2.16.0-22.redhat_00057.1.el7eap | RHSA-2026:53644 |
Frequently Asked Questions
Is CVE-2026-5588 in your dependencies?
O3 Security finds CVE-2026-5588 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.