Improper Verification of Cryptographic Signature in Bouncy Castle for Java and Bouncy Castle for Java LTS - CVE-2026-12803

Vulnerability identifier: #VU146438

CSH Severity: Medium

CVSS v4: 8.7 [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]

CVE-ID: CVE-2026-12803

CWE-ID: CWE-347

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to forge authenticated ciphertexts across nonces.

The vulnerability exists due to improper cryptographic binding in KCCMBlockCipher MAC processing when AAD is absent. A remote attacker can craft data that exploits the missing nonce binding to forge authenticated ciphertexts across nonces.

Bouncy Castle for Java
Bouncy Castle for Java LTS
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Real Time 15
Development Tools Module
Bamboo Data Center
bouncycastle-pkix
bouncycastle
bouncycastle-pg
bouncycastle-util

Install security update from vendor's website.

Bouncy Castle for Java - update to 1.85
Bouncy Castle for Java LTS - update to 2.73.12
Bamboo Data Center - addressed in versions 10.2.22, 12.1.10
bouncycastle-pkix - update to 1.85-150200.3.38.1
bouncycastle - update to 1.85-150200.3.38.1
bouncycastle-pg - update to 1.85-150200.3.38.1
bouncycastle-util - update to 1.85-150200.3.38.1

• https://www.openwall.com/lists/oss-security/2026/08/04/2
• https://www.bouncycastle.org/resources/new-release-bouncy-castle-java-1-85/

• Multiple vulnerabilities in Bouncy Castle Java
• Multiple vulnerabilities in Bamboo Data Center
• SUSE update for bouncycastle