CVE-2026-59640

Analyzed Analyzed - Analysis Complete

OpenPGP CFB Oracle in Bouncy Castle Java

Publication date: 2026-08-03

Last updated on: 2026-08-28

Assigner: bcorg

Description

In Bouncy Castle for Java before 1.85, OpenPGP CFB quick-check oracle active on symmetric/session-key paths. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bcpg-fips 1.0.13 (1.0.X series), 2.0.13 (2.0.X series) and 2.1.13 (2.1.X series).

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-03

Last Modified

2026-08-28

Generated

2026-09-12

AI Q&A

2026-08-03

EPSS Evaluated

2026-09-11

NVD

CVE-2026-59640

EUVD

EUVD-2026-52034

Affected Vendors & Products

Vendor	Product	Version / Range
bouncycastle	bc-java	to 1.85 (exc)
bouncycastle	bouncy_castle_for_java_lts	to 2.73.11 (inc)
bouncycastle	bcpg-fips	to 1.0.13 (exc)
bouncycastle	bcpg-fips	From 2.0.8 (inc) to 2.0.13 (exc)
bouncycastle	bcpg-fips	From 2.1.10 (inc) to 2.1.13 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-203	The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.

Attack-Flow Graph

Executive Summary

This vulnerability in Bouncy Castle for Java versions before 1.85 and related LTS/FIPS versions allows an attacker to use a quick-check oracle on OpenPGP CFB symmetric/session-key paths. This means an attacker could potentially exploit weaknesses in the encryption process to gain unauthorized access to encrypted data.

Detection Guidance

This vulnerability involves a quick-check oracle in OpenPGP CFB mode for symmetric/session-key paths in Bouncy Castle libraries. Detection requires checking the installed version of Bouncy Castle libraries against the affected versions (before 1.85 for mainline, before 2.73.12 for LTS, or specific versions for BC-FJA). Use commands like 'mvn dependency:tree' for Java projects or inspect package managers to verify versions.

Impact Analysis

If you use affected versions of Bouncy Castle for Java, this vulnerability could allow attackers to decrypt sensitive data, including communications or stored files protected by OpenPGP encryption. This may lead to data breaches, unauthorized access to confidential information, or loss of data integrity.

Compliance Impact

This vulnerability involves a quick-check oracle in OpenPGP CFB encryption paths, which could allow attackers to exploit weaknesses in symmetric/session-key handling. Such cryptographic flaws may undermine data confidentiality, a core requirement for GDPR and HIPAA compliance. Organizations using affected Bouncy Castle versions risk non-compliance due to potential unauthorized data access or exposure.

Mitigation Strategies

Upgrade Bouncy Castle for Java to version 1.85 or later. For LTS versions, upgrade to 2.73.12 or later. For BC-FJA, upgrade to bcpg-fips 1.0.13, 2.0.13, or 2.1.13 depending on your series.

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