High CVSS 8.7

CVE-2026-12803

NVD analysis in progress

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.

What this means

Exposure: Exploitable remotely over the network, without authentication and with no action from the victim.
Impact: An attacker can modify or destroy data.
Likelihood: Its EPSS score stays low: nothing points to imminent exploitation, which is no reason to leave it unpatched.

What to doFold into the next patch cycle. Start with the instances exposed to the internet.

Read automatically from the CVSS vector, the weakness type (CWE) and the EPSS score. The technical description above remains the one published by NIST.

Published: 3 August 2026
CVSS: 8.7 (v4.0) 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
EPSS: 0.17% probability of exploitation within 30 days · above 6% of all CVEs
Weakness: CWE-354
Sources: nvd

References

https://nvd.nist.gov/vuln/detail/CVE-2026-12803