BC-JAVA: Improper Verification of Cryptographic Signature
CVE-2026-59639 is a high-severity improper verification of cryptographic signature vulnerability in BC-JAVA from Legion of the Bouncy Castle, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 1.85 as the first without the flaw, so updating BC-JAVA to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.2% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update BC-JAVA to 1.85 or a later version.
- Update BC-LTS-JAVA to 2.73.12 or a later version.
- Update BC-FJA to 1.0.12 or 2.0.12 or 2.1.12, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Legion of the Bouncy Castle | BC-JAVA | before 1.85 | 1.85 |
| Legion of the Bouncy Castle | BC-LTS-JAVA | 2.73.0 up to, but not including, 2.73.12 | 2.73.12 |
| Legion of the Bouncy Castle | BC-FJA | 1.0.0 up to, but not including, 1.0.12; 2.0.0 up to, but not including, 2.0.12; 2.1.0 up to, but not including, 2.1.12 | 1.0.12, 2.0.12, 2.1.12 |
| Bouncycastle | Bcpkix-fips | before 1.0.12; 2.0.7 up to, but not including, 2.0.12; 2.1.8 up to, but not including, 2.1.12 | 1.0.12, 2.0.12, 2.1.12 |
| Bouncycastle | Bouncy Castle For Java LTS | 2.73.11 and earlier | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.7 | High | CNA |
| CVSS 3.1 | 7.5 | High | NVD |
Official description
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).
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Verification of Cryptographic Signature
The product does not verify, or incorrectly verifies, the cryptographic signature for data.
More Improper Verification of Cryptographic Signature vulnerabilities (CWE-347)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Third-party and government advisories
- github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059639Third Party Advisory
Other vulnerabilities in BC-JAVA
- 8.2 High severity
- 7.1 High severity
- 8.7 High severity
- 8.7 High severity
- 8.7 High severity
- 8.2 High severity
Recent Improper Verification of Cryptographic Signature vulnerabilities
- 9.2 Critical severity
- 7.5 High severity
- 9.1 Critical severity
- 9.8 Critical severity
- 8.1 High severity
- 7.5 High severity
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