CVE-2026-12802

Analyzed Analyzed - Analysis Complete

CMS AuthEnvelopedData Tag-Length Validation Bypass in Bouncy Castle for Java

Publication date: 2026-08-03

Last updated on: 2026-09-02

Assigner: bcorg

Description

In Bouncy Castle for Java before 1.85, CMS AuthEnvelopedData fails to enforce tag-length on decryption. 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).

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-03

Last Modified

2026-09-02

Generated

2026-09-12

AI Q&A

2026-08-03

EPSS Evaluated

2026-09-11

NVD

CVE-2026-12802

EUVD

EUVD-2026-52133

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	bcpkix-fips	to 1.0.12 (exc)
bouncycastle	bcpkix-fips	From 2.1.8 (inc) to 2.1.12 (exc)
bouncycastle	bcpkix-fips	From 2.0.7 (inc) to 2.0.12 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-354	The product does not validate or incorrectly validates the integrity check values or "checksums" of a message. This may prevent it from detecting if the data has been modified or corrupted in transmission.

Attack-Flow Graph

Executive Summary

In Bouncy Castle for Java versions before 1.85, the CMS AuthEnvelopedData component fails to enforce tag-length validation during decryption. This means an attacker could exploit this flaw to decrypt encrypted data without proper authentication or integrity checks.

Detection Guidance

This vulnerability affects Bouncy Castle for Java and related FIPS versions. Detection involves checking installed versions of Bouncy Castle libraries. Use commands like 'mvn dependency:tree' for Maven projects or 'gradle dependencies' for Gradle projects to inspect dependencies. Compare versions against the patched releases (1.85 for main, 2.73.12 for LTS, or FIPS series 1.0.12/2.0.12/2.1.12).

Impact Analysis

This vulnerability could allow unauthorized decryption of sensitive data protected by CMS AuthEnvelopedData. If exploited, attackers might access confidential information such as messages or files that were meant to be secure.

Compliance Impact

This vulnerability in Bouncy Castle's CMS AuthEnvelopedData could potentially allow unauthorized decryption of sensitive data due to improper tag-length enforcement. This may lead to data breaches, which could violate compliance requirements under GDPR (data protection) and HIPAA (healthcare data security).

Mitigation Strategies

Update 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 bcpkix-fips 1.0.12, 2.0.12, or 2.1.12 depending on your series.

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