Advisory details:
gitlab / maven/org.bouncycastle/bcprov-lts8on/CVE-2026-12803
| Advisory ID | gitlab/maven/org.bouncycastle/bcprov-lts8on/CVE-2026-12803 |
| Aliases |
CVE-2026-12803
|
| Summary | KCCMBlockCipher MAC does not bind nonce when AAD is absent (cross-nonce AEAD forgery) Affects Bouncy Castle for Java LTS before 2.73.12. DSTU 7624 CCM mode folds the nonce into the MAC block only inside processAAD(), which is skipped when no associated data is present. Without AAD the MAC is a zero-IV CBC-MAC over the plaintext alone, so tags do not depend on the nonce. A chosen-plaintext attacker can derive the keystreams for two nonces in three oracle queries and forge a valid ciphertext and tag for any unqueried plaintext and nonce, defeating authenticity. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 0.0 |
| Risk | |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | https://gitlab.com/gitlab-org/advisories-community/-/blob/main/maven/org.bouncycastle/bcprov-lts8on/CVE-2026-12803.yml |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
There are no SSVC decisions available.