OpenPGP CFB Quick-Check Oracle Vulnerability in Bouncy Castle for Java
CVE-2026-59640

8.7HIGH

Key Information:

Vendor

Legion Of The Bouncy Castle Inc.

Status
Bc-java
Bc-lts-java
Bc-fja
Vendor
CVE Published:
3 August 2026

What is CVE-2026-59640?

A flaw in the Bouncy Castle for Java library affects the OpenPGP implementation, where an oracle vulnerability exists in the CFB mode of symmetric and session-key paths. This vulnerability could allow attackers to conduct certain cryptographic attacks, potentially compromising the integrity of encrypted data. The issue spans multiple versions, including those prior to 1.85, and several LTS and FIPS releases, highlighting the need for immediate attention and remediation.

Affected Version(s)

BC-FJA all 1.0.0 < 1.0.13

BC-FJA all 2.0.0 < 2.0.13

BC-FJA all 2.1.0 < 2.1.13

References

https://github.com/bcgit/bc-java/wiki/CVE-2026-59640
vendor-advisory
https://github.com/bcgit/bc-java/commit/6b94b1c146cec1f56...
patch

CVSS V4

Score:
8.7
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Alex Gaynor in collaboration with Claude and Anthropic Research
.