CVE-2026-59642

CMS AuthenticatedData content not bound to MAC when authAttrs present

Published Aug 3, 2026 CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed

Description

In Bouncy Castle for Java before 1.85, CMS AuthenticatedData content not bound to MAC when authAttrs present. 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).

Analysis

Technical impact

In Bouncy Castle libraries for Java, the CMS AuthenticatedData formatter fails to include the content in the Message Authentication Code when authentication attributes are present. This flaw allows an attacker to alter authenticated data without causing MAC verification failure, effectively bypassing integrity checks and enabling data tampering or forging of authenticated messages.

Affected Systems

Legion of the Bouncy Castle Inc. products are affected: Bouncy Castle for Java (BC-JAVA) prior to version 1.85, Bouncy Castle for Java LTS (BC-LTS-JAVA) prior to 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) prior to bcpkix-fips 1.0.12, 2.0.12, and 2.1.12.

Risk and Exploitability

The vulnerability carries a CVSS score of 8.7, indicating a high severity for integrity loss. EPSS data is not available, and the issue is not listed in the CISA KEV catalog. Exploitation would require that an attacker can supply or modify CMS AuthenticatedData objects processed by the affected library, which could happen in applications that perform cryptographic signing or authentication. Because the MAC is not bound to the content, forged or tampered messages may be authenticated successfully, leading to potential loss of data integrity and reliance on compromised data.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Legion of the Bouncy Castle Inc.

BC-JAVA

unaffected

Version	Status	Constraints
`0`	affected	< 1.85

Legion of the Bouncy Castle Inc.

BC-LTS-JAVA

unaffected

Version	Status	Constraints
`2.73.0`	affected	< 2.73.12

Legion of the Bouncy Castle Inc.

BC-FJA

unaffected

Version	Status	Constraints
`1.0.0`	affected	< 1.0.12
`2.0.0`	affected	< 2.0.12
`2.1.0`	affected	< 2.1.12

Configuration 1 [-]

OR	cpe:2.3:a:bouncycastle:bc-java::::::::
	cpe:2.3:a:bouncycastle:bcpkix-fips::::::::
	cpe:2.3:a:bouncycastle:bcpkix-fips::::::::
	cpe:2.3:a:bouncycastle:bcpkix-fips::::::::
	cpe:2.3:a:bouncycastle:bouncy_castle_for_java_lts::::::::

No data.

Vendor Product Versions

Legion Of The Bouncy Castle Inc.

Bc-fja

Version	Status	Scheme	Platform
`[1.0.0,1.0.12)`	affected	semver	['all']
`[2.0.0,2.0.12)`	affected	semver	['all']
`[2.1.0,2.1.12)`	affected	semver	['all']

Legion Of The Bouncy Castle Inc.

Bc-java

Version	Status	Scheme	Platform
`[0,1.85)`	affected	generic	['all']

Legion Of The Bouncy Castle Inc.

Bc-lts-java

Version	Status	Scheme	Platform
`[2.73.0,2.73.12)`	affected	semver	['all']

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade all Bouncy Castle for Java libraries to the latest available versions: BC-JAVA 1.85 or newer, BC-LTS-JAVA 2.73.12 or newer, and BC-FJA to bcpkix-fips 1.0.12, 2.0.12, or 2.1.12 and later.
Audit and modify any application code that constructs or verifies CMS AuthenticatedData to ensure it uses the updated library and that the MAC calculation correctly includes the content; verify that all dependent libraries are also updated.
If immediate upgrade is not feasible, restrict the acceptance of CMS AuthenticatedData objects to trusted internal sources only, disable or reject authentication attributes in legacy code, and monitor for anomalous message modifications.

Generated by OpenCVE AI on August 4, 2026 at 10:55 UTC.

Tracking

Advisories

No advisories available

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact High

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.303% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact partial

References

Link	Providers
https://github.com/bcgit/bc-java/commit/2117f316a5a47308f3e569695a6592b16aac0dd7
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059642

History

Aug 28, 2026 6:30 PM First appearance in the feed. Affected versions updated. Affected vendors updated. Scoring metrics updated View changes

Type	Values Removed	Values Added
First Time appeared		Bouncycastle Bouncycastle bc-java Bouncycastle bcpkix-fips Bouncycastle bouncy Castle For Java Lts
CPEs		cpe:2.3:a:bouncycastle:bc-java:::::::: cpe:2.3:a:bouncycastle:bcpkix-fips:::::::: cpe:2.3:a:bouncycastle:bouncy_castle_for_java_lts::::::::
Vendors & Products		Bouncycastle Bouncycastle bc-java Bouncycastle bcpkix-fips Bouncycastle bouncy Castle For Java Lts
Metrics		cvssV3_1 `{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}`

Aug 3, 2026 4:15 PM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Legion Of The Bouncy Castle Inc. Legion Of The Bouncy Castle Inc. bc-fja Legion Of The Bouncy Castle Inc. bc-java Legion Of The Bouncy Castle Inc. bc-lts-java
Vendors & Products		Legion Of The Bouncy Castle Inc. Legion Of The Bouncy Castle Inc. bc-fja Legion Of The Bouncy Castle Inc. bc-java Legion Of The Bouncy Castle Inc. bc-lts-java

Aug 3, 2026 2:30 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Aug 3, 2026 5:30 AM References updated View changes

Type	Values Removed	Values Added
References	https://github.com/bcgit/bc-java/wiki/CVE-2026-59642	https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059642

Aug 3, 2026 1:15 AM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Description		In Bouncy Castle for Java before 1.85, CMS AuthenticatedData content not bound to MAC when authAttrs present. 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).
Title		CMS AuthenticatedData content not bound to MAC when authAttrs present
Weaknesses		CWE-354
References		https://github.com/bcgit/bc-java/commit/2117f316a5a47308f3e569695a6592b16aac0dd7 https://github.com/bcgit/bc-java/wiki/CVE-2026-59642
Metrics		cvssV4_0 `{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber'}`