CVE-2026-108109 Vulnerability Analysis & Exploit Details

CVE-2026-108109 Vulnerability Summary

CVE-2026-108109: PHPNuxBill through 2025.3.20 contains an account takeover vulnerability in the customer password reset flow in system/controllers/forgot.php that allows unauthenticated attackers to brute-force the 6-digit otp_code. Attackers knowing a customer username can guess the code without attempt limits or lockout, then read the newly set password from the HTTP response to hijack the account.

CVE-2026-108109 References

External References

• https://github.com/hotspotbilling/phpnuxbill
• https://github.com/hotspotbilling/phpnuxbill/blob/2025.3.13/system/controllers/forgot.php#L41
• https://github.com/hotspotbilling/phpnuxbill/commit/c3c2a92d468af91136d747b75142ed72f10320cc
• https://github.com/hotspotbilling/phpnuxbill/security/advisories/GHSA-337r-rrrc-r559
• https://www.vulncheck.com/advisories/phpnuxbill-through-2025.3.20-account-takeover-via-brute-forceable-password-reset-code

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Dictionary-based Password Attack CAPEC-16 An attacker tries each of the words in a dictionary as passwords to gain access to the system via some user's account. If the password chosen by the user was a word within the dictionary, this attack will be successful (in the absence of other mitigations). This is a specific instance of the password brute forcing attack pattern. Dictionary Attacks differ from similar attacks such as Password Spraying (CAPEC-565) and Credential Stuffing (CAPEC-600), since they leverage unknown username/password combinations and don't care about inducing account lockouts.
• Password Brute Forcing CAPEC-49 An adversary tries every possible value for a password until they succeed. A brute force attack, if feasible computationally, will always be successful because it will essentially go through all possible passwords given the alphabet used (lower case letters, upper case letters, numbers, symbols, etc.) and the maximum length of the password.
• Use of Known Domain Credentials CAPEC-560 An adversary guesses or obtains (i.e. steals or purchases) legitimate credentials (e.g. userID/password) to achieve authentication and to perform authorized actions under the guise of an authenticated user or service.
• Password Spraying CAPEC-565 In a Password Spraying attack, an adversary tries a small list (e.g. 3-5) of common or expected passwords, often matching the target's complexity policy, against a known list of user accounts to gain valid credentials. The adversary tries a particular password for each user account, before moving onto the next password in the list. This approach assists the adversary in remaining undetected by avoiding rapid or frequent account lockouts. The adversary may then reattempt the process with additional passwords, once enough time has passed to prevent inducing a lockout.
• Credential Stuffing CAPEC-600 An adversary tries known username/password combinations against different systems, applications, or services to gain additional authenticated access. Credential Stuffing attacks rely upon the fact that many users leverage the same username/password combination for multiple systems, applications, and services.
• Use of Known Kerberos Credentials CAPEC-652 An adversary obtains (i.e. steals or purchases) legitimate Kerberos credentials (e.g. Kerberos service account userID/password or Kerberos Tickets) with the goal of achieving authenticated access to additional systems, applications, or services within the domain.
• Use of Known Operating System Credentials CAPEC-653 An adversary guesses or obtains (i.e. steals or purchases) legitimate operating system credentials (e.g. userID/password) to achieve authentication and to perform authorized actions on the system, under the guise of an authenticated user or service. This applies to any Operating System.

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