CVE-2026-12816: CWE-354 Improper Validation of Integrity Check Value in Legion of the Bouncy Castle Inc. BC-JAVA
In Bouncy Castle for Java before 1.85, IESEngine stream-mode MAC forgery via length-dependent KDF split. This issue also affects Bouncy Castle for Java LTS before 2.73.12.
AI Analysis
Technical Summary
This vulnerability (CWE-354) in BC-JAVA's IESEngine stream-mode MAC implementation allows an attacker to forge message authentication codes due to improper validation of the integrity check value. The flaw arises from a length-dependent key derivation function split, which compromises the integrity protection mechanism. Affected versions include all releases before 1.85 and the LTS branch from 2.73.0 up to 2.73.12. The CVSS 4.0 base score is 8.7, indicating a high severity with network attack vector, no required privileges or user interaction, and high impact on integrity.
Potential Impact
Successful exploitation enables an attacker to forge MACs, potentially allowing tampering with data integrity protected by the IESEngine stream-mode MAC in affected BC-JAVA versions. This undermines the cryptographic assurances provided by the library, possibly leading to unauthorized data modification without detection.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is currently documented. Users should monitor the Legion of the Bouncy Castle Inc. advisories for updates and apply patches once available. Until then, avoid using affected versions in security-critical environments.
CVE-2026-12816: CWE-354 Improper Validation of Integrity Check Value in Legion of the Bouncy Castle Inc. BC-JAVA
Description
In Bouncy Castle for Java before 1.85, IESEngine stream-mode MAC forgery via length-dependent KDF split. This issue also affects Bouncy Castle for Java LTS before 2.73.12.
CVSS v4.0
Score 8.7high
Affected software
pkg:github/bcprov-lts8onRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CWE-354) in BC-JAVA's IESEngine stream-mode MAC implementation allows an attacker to forge message authentication codes due to improper validation of the integrity check value. The flaw arises from a length-dependent key derivation function split, which compromises the integrity protection mechanism. Affected versions include all releases before 1.85 and the LTS branch from 2.73.0 up to 2.73.12. The CVSS 4.0 base score is 8.7, indicating a high severity with network attack vector, no required privileges or user interaction, and high impact on integrity.
Potential Impact
Successful exploitation enables an attacker to forge MACs, potentially allowing tampering with data integrity protected by the IESEngine stream-mode MAC in affected BC-JAVA versions. This undermines the cryptographic assurances provided by the library, possibly leading to unauthorized data modification without detection.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is currently documented. Users should monitor the Legion of the Bouncy Castle Inc. advisories for updates and apply patches once available. Until then, avoid using affected versions in security-critical environments.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- bcorg
- Date Reserved
- 2026-06-21T08:41:26.174Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a701320bf32cb7a34eafeb1
Added to database: 08/03/2026, 04:03:44 UTC
Last enriched: 08/03/2026, 04:18:30 UTC
Last updated: 08/03/2026, 19:34:42 UTC
Views: 4
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