BC-JAVA: Improper Verification of Cryptographic Signature
CVE-2026-59643 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 0.24% 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-FJA to 2.0.13 or a later version.
- Update Bcpg-fips to 2.0.13 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 | 1.81 up to, but not including, 1.85 | 1.85 |
| Legion of the Bouncy Castle | BC-FJA | 2.0.12 up to, but not including, 2.0.13 | 2.0.13 |
| Bouncycastle | Bcpg-fips | before 2.0.13 | 2.0.13 |
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, OpenPGP inline-signature policy failures silently ignored. This issue also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpg-fips 2.0.13.
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%9059643Third 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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