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Java CVE-2026-5588

| EUVDEUVD-2026-22871 MEDIUM
Use of a Broken or Risky Cryptographic Algorithm (CWE-327)
2026-04-15 bcorg GHSA-wg6q-6289-32hp
Java Information Disclosure Bc Java
6.3
CVSS 4.0 · Vendor: bcorg
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Severity by source

Vendor (bcorg) PRIMARY
6.3 MEDIUM
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
SUSE
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (bcorg).

CVSS VectorVendor: bcorg

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

8
Patch released
Apr 21, 2026 - 16:16 nvd
Patch available
Patch available
Apr 16, 2026 - 05:29 EUVD
1.84
Severity Changed
Apr 15, 2026 - 17:22 NVD
CRITICAL MEDIUM
CVSS changed
Apr 15, 2026 - 17:22 NVD
10.0 (CRITICAL) 6.3 (MEDIUM)
Analysis Generated
Apr 15, 2026 - 12:38 vuln.today
EUVD ID Assigned
Apr 15, 2026 - 09:30 euvd
EUVD-2026-22871
Analysis Generated
Apr 15, 2026 - 09:30 vuln.today
CVE Published
Apr 15, 2026 - 09:06 nvd
MEDIUM 6.3

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 437 maven packages depend on org.bouncycastle:bcpkix-jdk15on (84 direct, 354 indirect)

Ecosystem-wide dependent count for version 1.49.

DescriptionCVE.org

: 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.

AnalysisAI

Signature verification bypass in Bouncy Castle BC-JAVA (bcpkix module versions 1.49-1.83) allows remote unauthenticated attackers to forge cryptographic signatures by submitting empty signature sequences that are incorrectly accepted as valid by the draft CompositeVerifier implementation. This critical flaw (CVSS 4.0: 10.0) enables complete subversion of digital signature trust chains, potentially allowing authentication bypass, code signing forgery, and man-in-the-middle attacks against Java ap

Technical ContextAI

Bouncy Castle BC-JAVA is a widely-adopted cryptographic library providing Java implementations of cryptographic algorithms and PKIX (Public Key Infrastructure using X.509) certificate handling. The vulnerability resides in the bcpkix module's draft CompositeVerifier, which implements composite signature schemes per draft IETF standards. CWE-327 (Use of Broken or Risky Cryptographic Algorithm) classifies this as a cryptographic implementation flaw where the verifier incorrectly validates an empty signature sequence - a fundamental violation of cryptographic verification principles. In proper signature verification, an empty signature should always fail validation since it provides no cryptographic proof of origin or integrity. The CompositeVerifier's acceptance of null/empty signatures effectively bypasses the entire signature validation process, rendering cryptographic protections meaningless. Affected product CPE: cpe:2.3:a:legion_of_the_bouncy_castle_inc.:bc-java:*:*:*:*:*:*:*:* spanning versions 1.49 through 1.83 across all deployment platforms.

RemediationAI

Immediately upgrade Bouncy Castle BC-JAVA to version 1.84 or later, which addresses the empty signature acceptance flaw in the CompositeVerifier implementation. Organizations should inventory all Java applications and dependencies for BC-JAVA versions 1.49-1.83, prioritizing internet-facing services and applications performing certificate validation or signature verification. Update dependencies in build configurations (Maven pom.xml, Gradle build files) to bc-java:1.84+ and redeploy affected applications. If immediate upgrade is blocked by compatibility testing requirements, implement temporary workaround by avoiding use of the draft CompositeVerifier API and reverting to production-grade signature verification methods in Bouncy Castle's standard PKIX implementation. Conduct post-remediation verification to confirm no historical signature forgery has occurred by reviewing authentication logs and certificate validation audit trails for anomalous patterns. Complete vendor security advisory and patch details available at https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%905588. No workarounds can fully mitigate the risk if CompositeVerifier is actively used in production code paths.

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected
SUSE Linux Enterprise Module for Development Tools 15 SP7 Affected

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CVE-2026-5588 vulnerability details – vuln.today
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