In Bouncy Castle for Java before 1.85, KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery). This issue also affects Bouncy Castle for Java LTS before 2.73.12.

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

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00174.

Key SSVC decision points have not yet been added.

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

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Project Subscriptions

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Advisories

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Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/bcgit/bc-java/commit/697794413ebf7bc5e3fce609a707826ba52981af cve-icon
https://github.com/bcgit/bc-java/commit/7d79aa76e984da85f2a541cae8ba2ae56e1713bc cve-icon
https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9012803 cve-icon
History

Mon, 03 Aug 2026 06:45:00 +0000

Type Values Removed Values Added
References

Mon, 03 Aug 2026 04:00:00 +0000

Type Values Removed Values Added
Description In Bouncy Castle for Java before 1.85, KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery). This issue also affects Bouncy Castle for Java LTS before 2.73.12.
Title KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery)
Weaknesses CWE-354
References
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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: bcorg

Published:

Updated: 2026-08-03T05:58:49.795Z

Reserved: 2026-06-21T01:50:45.847Z

Link: CVE-2026-12803

cve-icon Vulnrichment

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cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

Updated: 2026-08-03T09:00:15Z

Weaknesses