Bouncycastle: In Bouncy Castle for Java before 1.85, CMS verifySignatures returns true for SignedData with zero signers. (CVE-2026-59639)
Description
Bouncy Castle for Java versions before 1.85 have a vulnerability where the CMS verifySignatures method returns true even when SignedData contains zero signers. This affects multiple Bouncy Castle Java variants, including LTS and FIPS versions prior to specific releases. The issue could lead to improper signature verification results.
CVSS v3.1
Score 7.5high
Affected software
pkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps/xenialpkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps/bionicpkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps/focalpkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps/jammypkg:deb/ubuntu/bouncycastle?arch=source&distro=esm-apps/noblepkg:deb/ubuntu/bouncycastle?arch=source&distro=stonkingpkg:deb/ubuntu/bouncycastle?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in Bouncy Castle for Java prior to version 1.85 causes the CMS verifySignatures method to incorrectly return true when verifying SignedData objects that have no signers. This flaw is also present in Bouncy Castle for Java LTS versions before 2.73.12 and Bouncy Castle for Java FIPS versions 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). The incorrect verification result could allow an attacker to bypass signature validation checks under certain conditions.
Potential Impact
The vulnerability allows the verifySignatures method to indicate a successful signature verification even when no signers are present in the SignedData. This can lead to a false sense of data integrity and authenticity, potentially enabling attackers to bypass signature verification controls. The CVSS 3.1 score is 7.5 (High impact on integrity, no impact on confidentiality or availability).
Mitigation Recommendations
A fix is available in Bouncy Castle for Java version 1.85 and later, Bouncy Castle for Java LTS version 2.73.12 and later, and Bouncy Castle for Java FIPS versions bcpkix-fips 1.0.12 (1.0.X series), 2.0.12 (2.0.X series), and 2.1.12 (2.1.X series) or later. Users should upgrade to these fixed versions to resolve the issue. No vendor advisory content was provided to indicate alternative mitigations or temporary fixes.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-59639
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:Pro:22.04:LTS","Ubuntu:Pro:24.04:LTS","Ubuntu:26.10","Ubuntu:26.04:LTS"]
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ad3f5da2cdf04f656663251
Added to database: 10/17/2026, 22:25:30 UTC
Last enriched: 10/18/2026, 00:30:37 UTC
Last updated: 10/18/2026, 00:30:37 UTC
Views: 2
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