CVE-2026-46395 in haxcms-nodejs
Summary
by MITRE • 06/05/2026
HAX CMS helps manage microsite universe with PHP or NodeJs backends. Prior to version 26.0.0, the `hmacBase64()` function in the HAXcms Node.js backend contains two critical cryptographic implementation errors that together allow any unauthenticated attacker to extract the system’s private signing key and forge arbitrary admin-level JSON Web Tokens (JWTs) allowing them to get full admin access with a single HTTP request. First, the function passes the literal string "0" as the HMAC signing key instead of the key parameter, making every HAXcms instance compute identical HMACs for the same input. Then, after computing the HMAC, the function concatenates the real key parameter which is "this.privateKey + this.salt", the system’s master signing secret is directly onto the output. The combined buffer is base64-encoded and returned as the token. Every base64url token produced has the same structure: 32 bytes HMAC keyed with "0" and N bytes of `privateKey+salt`. An attacker base64-decodes any token, discards the first 32 bytes, and reads the private key directly. The `/system/api/connectionSettings` endpoint is unauthenticated and returns multiple tokens generated by this function. A single GET request to this endpoint exposes the private key. The PHP backend implements this function correctly with the actual key and returns only the hash. The PHP version produces 44-character tokens whereas the broken Node.js version produces 139+ character tokens. Version 26.0.0 fixes the issue.
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Analysis
by VulDB Data Team • 06/05/2026
The HAX CMS vulnerability represents a critical cryptographic flaw in the Node.js backend that fundamentally undermines the security of the entire system. This vulnerability affects versions prior to 26.0.0 and stems from a fundamental error in the hmacBase64() function implementation. The flaw manifests in two interconnected cryptographic failures that together create a complete compromise of the authentication system. The first error occurs when the function incorrectly passes the literal string "0" as the HMAC signing key instead of utilizing the intended key parameter. This fundamental mistake means that every HAXcms instance computes identical HMAC values for the same input, completely eliminating the cryptographic security that should be provided by unique keys. The second error compounds this issue by concatenating the actual private key parameter, which consists of "this.privateKey + this.salt", directly onto the HMAC output before base64 encoding. This concatenation creates a situation where the private key becomes directly exposed within the token structure, making it trivial for attackers to extract sensitive information.
The operational impact of this vulnerability is devastating and requires no special privileges or complex attack vectors to exploit. An unauthenticated attacker can simply make a single GET request to the unauthenticated /system/api/connectionSettings endpoint to obtain multiple tokens generated by the flawed function. These tokens contain the complete private signing key within their structure, specifically in the base64url-encoded output where the first 32 bytes represent the HMAC keyed with "0" and the remaining bytes contain the concatenated private key and salt. The difference in token length between the PHP implementation (44-character tokens) and the Node.js implementation (139+ character tokens) directly correlates to this vulnerability, with the Node.js version exposing the private key through its extended output structure. This vulnerability aligns with CWE-327 (Use of a Broken or Risky Cryptographic Algorithm) and CWE-324 (Use of a Key That Is Too Short) as it demonstrates both improper cryptographic implementation and the exposure of sensitive cryptographic material. The attack pattern follows ATT&CK technique T1566.001 (Phishing: Spearphishing Attachment) in its exploitation method, as attackers could potentially use this vulnerability to gain administrative access through a single HTTP request without requiring authentication.
The technical exploitation process is straightforward and highly effective due to the design flaws in the hmacBase64() function. When an attacker obtains a token from the /system/api/connectionSettings endpoint, they simply base64-decode the token and discard the first 32 bytes that represent the HMAC computed with the fixed key "0". The remainder of the decoded buffer contains the actual private key concatenated with the salt, which is then directly usable for forging administrative JWTs. This vulnerability essentially transforms the cryptographic system from a security mechanism into a key exposure vulnerability, where the very function designed to provide security becomes the mechanism for exposing the system's core secret. The fact that this vulnerability exists only in the Node.js backend while the PHP implementation correctly handles the cryptographic functions demonstrates a clear regression or implementation error that allowed the flawed code to persist. The fix in version 26.0.0 addresses both the incorrect HMAC key usage and the improper concatenation of the private key into the token output, restoring proper cryptographic security to the authentication system. This vulnerability serves as a prime example of how a single cryptographic implementation error can completely destroy the security model of an entire system, requiring immediate remediation for all affected installations.