CVE-2026-59639: CWE-347 Improper Verification of Cryptographic Signature in Legion of the Bouncy Castle Inc. BC-JAVA
Bouncy Castle for Java versions before 1.85 and certain 2.x LTS versions incorrectly verify cryptographic signatures in CMS SignedData objects with zero signers, causing verifySignatures to return true improperly. This vulnerability affects BC-JAVA and related FIPS versions. It is classified as CWE-347, indicating improper verification of cryptographic signatures.
AI Analysis
Technical Summary
CVE-2026-59639 is a vulnerability in Legion of the Bouncy Castle Inc.'s BC-JAVA library where the CMS verifySignatures method returns true for SignedData objects that contain zero signers. This flaw affects Bouncy Castle for Java versions prior to 1.85, LTS versions from 2.73.0 up to but not including 2.73.12, and certain BC-FJA FIPS series versions. The issue represents an improper verification of cryptographic signatures (CWE-347), potentially allowing acceptance of unsigned data as validly signed.
Potential Impact
The vulnerability allows cryptographic signature verification to succeed on CMS SignedData with no signers, which can lead to acceptance of unauthenticated or tampered data. This undermines the integrity guarantees expected from signature verification, potentially enabling attackers to bypass signature validation checks. The CVSS 4.0 score is 8.7 (high severity), indicating a significant security impact with network attack vector, no privileges or user interaction required, and high impact on integrity.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Users should monitor the Legion of the Bouncy Castle Inc. advisories for updates and apply patches once available. Until then, avoid relying on the verifySignatures method for CMS SignedData objects that may contain zero signers.
CVE-2026-59639: CWE-347 Improper Verification of Cryptographic Signature in Legion of the Bouncy Castle Inc. BC-JAVA
Description
Bouncy Castle for Java versions before 1.85 and certain 2.x LTS versions incorrectly verify cryptographic signatures in CMS SignedData objects with zero signers, causing verifySignatures to return true improperly. This vulnerability affects BC-JAVA and related FIPS versions. It is classified as CWE-347, indicating improper verification of cryptographic signatures.
CVSS v4.0
Score 8.7high
Affected software
pkg:github/bcpkix-lts8onRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-59639 is a vulnerability in Legion of the Bouncy Castle Inc.'s BC-JAVA library where the CMS verifySignatures method returns true for SignedData objects that contain zero signers. This flaw affects Bouncy Castle for Java versions prior to 1.85, LTS versions from 2.73.0 up to but not including 2.73.12, and certain BC-FJA FIPS series versions. The issue represents an improper verification of cryptographic signatures (CWE-347), potentially allowing acceptance of unsigned data as validly signed.
Potential Impact
The vulnerability allows cryptographic signature verification to succeed on CMS SignedData with no signers, which can lead to acceptance of unauthenticated or tampered data. This undermines the integrity guarantees expected from signature verification, potentially enabling attackers to bypass signature validation checks. The CVSS 4.0 score is 8.7 (high severity), indicating a significant security impact with network attack vector, no privileges or user interaction required, and high impact on integrity.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Users should monitor the Legion of the Bouncy Castle Inc. advisories for updates and apply patches once available. Until then, avoid relying on the verifySignatures method for CMS SignedData objects that may contain zero signers.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- bcorg
- Date Reserved
- 2026-07-06T06:58:29.263Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a6fe8f1bf32cb7a34b61c92
Added to database: 08/03/2026, 01:03:45 UTC
Last enriched: 08/03/2026, 01:19:53 UTC
Last updated: 08/03/2026, 02:08:26 UTC
Views: 4
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.