CVE-2026-5588
CVE-2026-5588 is a security vulnerability in org.bouncycastle:bcpkix-jdk18on. O3 Security confirms whether CVE-2026-5588 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
PKIX draft CompositeVerifier accepts empty signature sequence as valid.
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.
Blast Radius
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 | 1.84 |
| ☕Maven | org.bouncycastle:bcpkix-jdk15to18 | ≥ 1.49&&< 1.84 | 1.84 |
| ☕Maven | org.bouncycastle:bcpkix-jdk15on | ≥ 1.49&&< 1.84 | 1.84 |
| ☕Maven | org.bouncycastle:bcpkix-jdk14 | ≥ 1.49&&< 1.84 | 1.84 |
| ☕Maven | org.bouncycastle:bcpkix-debug-jdk18on | ≥ 1.49&&< 1.84 | 1.84 |
| ☕Maven | org.bouncycastle:bcpkix-debug-jdk15to18 | ≥ 1.49&&< 1.84 | 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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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 pinpoints whether CVE-2026-5588 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
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.
Frequently Asked Questions
Is CVE-2026-5588 in your dependencies?
O3 detects CVE-2026-5588 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.