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Bouncy Castle Java CVE-2026-59640

| EUVDEUVD-2026-52034 HIGH
Observable Discrepancy (CWE-203)
2026-08-03 bcorg GHSA-w983-hf44-gcww
Java Information Disclosure Oracle Bc Java Bc Lts Java Bc Fja
8.7
CVSS 4.0 · Vendor: bcorg
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Severity by source

Vendor (bcorg) PRIMARY
8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
vuln.today AI
5.9 MEDIUM

Adaptive chosen-ciphertext oracle requires many crafted submissions and distinguishable error visibility, warranting AC:H; no authentication needed to reach an exposed decryption service.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative

Primary rating from Vendor (bcorg).

CVSS VectorVendor: bcorg

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
Source Code Evidence Fetched
Aug 03, 2026 - 01:37 vuln.today
Analysis Generated
Aug 03, 2026 - 01:37 vuln.today
CVE Published
Aug 03, 2026 - 00:55 cve.org
HIGH 8.7

DescriptionCVE.org

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).

AnalysisAI

Bouncy Castle for Java's OpenPGP session-key decryption path re-exposes the Mister-Zuccherato adaptive-chosen-ciphertext oracle by failing to suppress the legacy CFB 'quick check' on the PKESK/session-key route, enabling an attacker with decryption oracle access to recover plaintext from SEIPD v1 encrypted messages. Affected are bc-java before 1.85, bc-lts-java before 2.73.12, and BC-FJA (bcpg-fips) across the 1.0.X, 2.0.X, and 2.1.X series - three distinct product lines used broadly in enterprise and open-source Java applications. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Locate network-accessible OpenPGP decryption endpoint
Delivery
Capture or synthesize target SEIPD v1 ciphertext
Exploit
Submit adaptively crafted ciphertexts to trigger quick-check oracle
Execution
Distinguish early PGPDataValidationException from MDC failure response
Persist
Iteratively recover plaintext bytes via Mister-Zuccherato technique
Impact
Exfiltrate decrypted message content
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Vulnerability AssessmentAI

Exploitation Exploitation requires the target application to use Bouncy Castle's OpenPGP high-level API on the session-key/PKESK decryption path (specifically PGPSessionKeyEncryptedData or equivalent code reaching the unpatched processSymmetricEncIntegrityPacketDataStream() in the affected versions) against SEIPD v1 formatted data. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The vendor-assigned CVSS 4.0 score of 8.7 (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H) reflects a network-accessible, unauthenticated path to high confidentiality impact, which is accurate for the general exposure model but arguably overstates attack simplicity. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker identifies a network-accessible Java service using Bouncy Castle's OpenPGP high-level API to decrypt PKESK-encrypted messages and submits a series of adaptively crafted SEIPD v1 ciphertexts, observing whether the service returns a quick-check exception (PGPDataValidationException before MDC) versus an MDC integrity failure. By iteratively refining chosen ciphertexts based on oracle responses - consistent with the Mister-Zuccherato technique - the attacker extracts plaintext bytes from intercepted legitimate encrypted messages. …
Remediation Upgrade to Bouncy Castle for Java 1.85 or later, Bouncy Castle LTS 2.73.12 or later, or BC-FJA bcpg-fips 1.0.13/2.0.13/2.1.13 (matching your installed 1.0.X/2.0.X/2.1.X series). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory all systems and applications running bc-java, bc-lts-java, or BC-FJA/bcpg-fips. …

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Threat intelligence, references, and detailed analysis are available after sign-in.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Module for Development Tools 15 SP7 Affected
SUSE Linux Enterprise Server 15 SP7 Affected
SUSE Linux Enterprise Server 16.0 Affected

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CVE-2026-59640 vulnerability details – vuln.today
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