Review reviewHigh

CVE-2026-59639

Legion of the Bouncy Castle Inc. BC-JAVA, BC-LTS-JAVA, BC-FJA

In Bouncy Castle for Java before 1.85, CMS verifySignatures returns true for SignedData with zero signers. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpkix-fips 1.0.12 (1.0.X series), 2.0.12 (2.0.X series) and 2.1.12 (2.1.X series).

CVSS: 8.7
EPSS: -
CISA KEV: Not listed
Published: 2026.08.03

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability-

Technical severityCVSS 8.7

Vulnerability overview

Affected product and versions

Product: Legion of the Bouncy Castle Inc. BC-JAVA, BC-LTS-JAVA, BC-FJA
Affected versions: < 1.85, >= 2.73.0 < 2.73.12, >= 1.0.0 < 1.0.12, >= 2.0.0 < 2.0.12, >= 2.1.0 < 2.1.12
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that Legion of the Bouncy Castle Inc. BC-JAVA, BC-LTS-JAVA, BC-FJA and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/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
CWE: CWE-347