CVE-2026-75431 in Server
Summary
by MITRE • 09/04/2026
PowerJob Server version 5.1.2 (and likely earlier) uses a predictable JWT signing key for HS256-based authentication. This allows a remote attacker to execute arbitrary code.
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Analysis
by VulDB Data Team • 09/05/2026
The vulnerability identified in PowerJob Server versions prior to or including 5.1.2 represents a critical failure in cryptographic implementation, specifically concerning the management of JSON Web Token (JWT) signing keys for HS256 authentication mechanisms. In secure software architecture, JWTs are commonly used as stateless tokens to authenticate users and authorize access to protected resources within distributed systems like PowerJob. The security model relies heavily on the secrecy and unpredictability of the symmetric key used to sign these tokens using the HMAC-SHA256 algorithm. When a server utilizes a predictable or hardcoded signing key, it fundamentally breaks this trust assumption, allowing any external actor who can observe valid traffic or access source code documentation to derive the secret key required to forge arbitrary JWTs.
From a technical perspective, HS256 requires that both the issuer and the verifier share the same secret key. If this key is static across deployments or derived from easily guessable patterns such as default strings like "secret" or common variable names found in configuration files, an attacker can perform offline brute-force attacks with near-zero computational cost to identify the specific key used by a target instance. Once the signing key is obtained, the attacker gains the ability to craft malicious JWTs that contain arbitrary claims. These forged tokens are accepted as valid by the server because they pass the cryptographic signature verification process, effectively bypassing all authentication controls without needing legitimate credentials or exploiting input validation flaws in traditional web forms.
The operational impact of this vulnerability is severe and directly leads to remote code execution (RCE) within the context of the PowerJob Server application. Since JWTs often carry user roles, permissions, and session identifiers, a forged token can be crafted with administrative privileges or elevated system rights. In distributed task scheduling platforms like PowerJob, authentication tokens are frequently used to authorize job submissions, configuration changes, and execution commands on worker nodes. By injecting a maliciously signed JWT that impersonates an administrator, an attacker can submit jobs containing payloads designed for code execution. This allows the remote exploitation of downstream components or direct command injection into the server environment, leading to full system compromise, data exfiltration, and potential lateral movement within the internal network infrastructure where PowerJob operates.
This flaw aligns with CWE-798: Use of Hard-coded Credentials, as it involves the use of a static secret that is not unique per deployment or difficult to guess. Furthermore, from an offensive security framework perspective, this vulnerability facilitates ATT&CK technique T1078: Valid Accounts and T1528: Steal Application Access Token, enabling attackers to establish persistent access by maintaining valid session tokens without detection through standard authentication logs. The lack of entropy in the key generation process violates fundamental principles outlined in OWASP guidelines for secure token management, which mandate that secrets must be generated using cryptographically strong random number generators and stored securely rather than being hardcoded or predictable.
Mitigation strategies require immediate remediation by upgrading to a patched version of PowerJob where this issue has been addressed through dynamic key generation or integration with external secret management systems such as HashiCorp Vault or AWS Secrets Manager. In the interim, administrators should enforce strict network segmentation to limit exposure of the PowerJob interface to untrusted networks and monitor authentication logs for anomalies indicative of token forgery attempts. Additionally, implementing Web Application Firewall rules that detect unusual JWT structures or unexpected claim values can provide a layer of defense-in-depth while permanent fixes are deployed. It is also critical to audit all configuration files and source code repositories to ensure no other hardcoded secrets remain in the deployment pipeline, as this vulnerability often indicates broader weaknesses in security hygiene regarding credential management practices.