CVE-2026-12816
Description
A flaw was found in Bouncy Castle for Java. This vulnerability allows for Message Authentication Code (MAC) forgery in the IESEngine stream-mode. The issue arises from a length-dependent Key Derivation Function (KDF) split, which an attacker could exploit to bypass integrity checks. This could lead to unauthorized manipulation of data.
Statement
This is an Important vulnerability. Bouncy Castle for Java is susceptible to Message Authentication Code (MAC) forgery in IESEngine stream-mode due to a length-dependent Key Derivation Function (KDF) split. An unauthenticated, remote attacker could exploit this flaw to compromise the integrity of data protected by the affected cryptographic operations.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Incorrect usage of crypto primitives could render the supposedly encrypted data as unencrypted plaintext in the worst case.
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