CVE-2025-51606: Critical Security Vulnerability in hippo4j Due to Hard-Coded JWT Secret Key

Overview

The Common Vulnerabilities and Exposures (CVE) system has recently identified a critical security vulnerability, designated as CVE-2025-51606, affecting versions 1.0.0 to 1.5.0 of the hippo4j software. This vulnerability, which pertains to the use of a hard-coded secret key in JWT (JSON Web Token) creation, poses a significant security risk to any systems where authentication and authorization rely heavily on the integrity of JWTs. If exploited, it could lead to system compromise or data leakage and, therefore, it is of paramount importance that users take immediate steps to mitigate the threat.

Vulnerability Summary

CVE ID: CVE-2025-51606
Severity: High (Score: 8.8)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

hippo4j | 1.0.0 to 1.5.0

How the Exploit Works

The vulnerability arises from the use of a hard-coded secret key for JWT creation in hippo4j. An attacker with access to the source code or compiled binary can exploit this vulnerability by forging valid access tokens and impersonating any user, even privileged ones such as “admin”. This allows the attacker to bypass authentication measures and gain unauthorized access to the system.

Conceptual Example Code

Here’s a conceptual example of how the vulnerability might be exploited. This is a pseudocode for creating a forged JWT:

# Import JWT library
import jwt
# Define hard-coded secret key
secret_key = "hard-coded-secret-key-from-hippo4j"
# Define malicious payload with admin privileges
malicious_payload = {
"user": "admin",
"privileges": "all"
}
# Forge JWT using the secret key and malicious payload
forged_token = jwt.encode(malicious_payload, secret_key, algorithm='HS256')
# Now the attacker can use this forged_token to impersonate as admin

Keep in mind that this is a hypothetical example and the actual code or method used by an attacker may vary based on the specific circumstances and the attacker’s knowledge and resources. Nonetheless, it demonstrates the potential severity and exploitability of the vulnerability.