CVE-2026-78062 in TaxHacker
Summary
by MITRE • 08/23/2026
A vulnerability was identified in vas3k TaxHacker up to 0.8.2. The affected element is the function envSchema.parse of the file lib/config.ts of the component JWT Secret Handler. The manipulation of the argument BETTER_AUTH_SECRET leads to hard-coded credentials. The attack can be initiated remotely. The project was informed of the problem early through an issue report but has not responded yet.
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Analysis
by VulDB Data Team • 08/23/2026
The vulnerability identified in vas3k TaxHacker versions up to 0.8.2 represents a critical configuration management flaw within the JWT Secret Handler component, specifically located in the envSchema.parse function found in lib/config.ts. This architectural weakness stems from how the application handles environment variables during its initialization phase. The core issue lies in the improper validation and processing of the BETTER_AUTH_SECRET argument. Instead of strictly enforcing that this secret must be provided via a secure external configuration source, such as an operating system environment variable or a dedicated secrets manager, the software logic allows for fallback behaviors or default assignments when specific conditions are met. This design oversight results in the application falling back to hard-coded credentials if the expected input is not correctly formatted or absent during runtime initialization.
From a technical perspective, this flaw constitutes a classic case of insecure configuration where sensitive cryptographic material is embedded directly within the source code rather than being managed dynamically and securely. The envSchema.parse function acts as the gatekeeper for application configuration but fails to adequately sanitize or validate the input stream for the BETTER_AUTH_SECRET parameter. Consequently, if an attacker can influence the context in which this function executes, they may trigger a state where the hard-coded default secret is utilized instead of a unique, randomly generated key known only to the deployment environment. This undermines the fundamental principle of defense-in-depth by removing the variability and secrecy required for robust JSON Web Token authentication mechanisms.
The operational impact of this vulnerability is severe due to its remote exploitability. Since JWTs are commonly used for stateless authentication in web applications, compromising the signing secret allows an attacker to forge valid tokens with arbitrary claims. An adversary could generate administrative access tokens, impersonate legitimate users, or escalate privileges within the application without needing prior credentials. Because the project has not yet responded to early issue reports regarding this problem, existing deployments remain exposed to potential exploitation. The persistence of hard-coded secrets also complicates incident response and remediation efforts, as rotating keys requires updating source code rather than simply changing environment variables, increasing the window of exposure during patching cycles.
This vulnerability aligns with CWE-798: Use of Hard-coded Credentials, which describes situations where authentication credentials are embedded in software, making them discoverable by attackers who gain access to the application binary or source code. Furthermore, it relates to CWE-215: Information Exposure Through Debugging Code if the fallback mechanism was intended for development environments but leaked into production configurations due to insufficient environment checks. In terms of offensive security frameworks, this flaw facilitates ATT&CK technique T1078: Valid Accounts, as attackers can create valid authentication tokens that bypass standard login procedures. It also touches upon T1529: System Shutdown or Reboot if the compromise leads to broader system control, though primarily it serves as an entry point for unauthorized access via credential forgery.
Mitigation strategies must prioritize immediate remediation of the configuration handling logic within lib/config.ts. Developers should ensure that envSchema.parse strictly rejects any attempt to use default values for critical secrets like BETTER_AUTH_SECRET in production environments. Implementing a fail-fast mechanism where the application refuses to start if essential cryptographic keys are not explicitly provided via secure channels is recommended. Additionally, organizations running affected versions should immediately rotate all JWT signing secrets and audit access logs for signs of token forgery or unauthorized administrative actions until an official patch is released by the vendor. Long-term fixes involve adopting a zero-trust configuration model where no sensitive data defaults to static values within the codebase itself.