CVE-2026-12803

HIGH

KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery)

Title source: cna
STIX 2.1

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.

References (4)

Core 4

Scores

CVSS v4 8.7
EPSS 0.0017
EPSS Percentile 7.0%
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact partial

Details

CWE
CWE-354
Status published
Products (2)
Legion of the Bouncy Castle Inc./BC-JAVA < 1.85
Legion of the Bouncy Castle Inc./BC-LTS-JAVA 2.73.0 - 2.73.12
Published Aug 03, 2026
Tracked Since Aug 03, 2026