CVE-2026-12860
Description
A flaw was found in Bouncy Castle for Java. During the RSA PKCS#1 verification process, the last two hash bytes are incorrectly skipped when a NULL-omitted path is utilized. This vulnerability could allow an attacker to bypass cryptographic signature verification, potentially leading to the acceptance of forged or malicious data as authentic.
Statement
A signature verification flaw was found in Bouncy Castle for Java's RSA PKCS#1 parser (bcprov). When verifying RSA PKCS#1 v1.5 signatures utilizing a NULL-omitted DigestInfo path, the verification routine incorrectly skips the last two bytes of the expected digest hash. An unauthenticated remote attacker can exploit this truncated comparison to craft forged signatures that pass verification, bypassing cryptographic integrity controls.
Mitigation
Enforce strict DigestInfo encoding checks requiring explicit ASN.1 NULL parameters in RSA PKCS#1 v1.5 signature verification, or mandate the use of RSA-PSS signature schemes in application TLS/crypto configuration.
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 | 5.3 | 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 | Low | 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:L/A:N
Understanding the Weakness (CWE)
Access Control,Integrity,Confidentiality
Technical Impact: Gain Privileges or Assume Identity; Modify Application Data; Execute Unauthorized Code or Commands
An attacker could gain access to sensitive data and possibly execute unauthorized code.
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