CVE-2026-108109: Brute Force (CVSS 9.1)

Description

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.

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CVSS v3.1 Score

9.1

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0039

Probability of exploitation

0.31%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-307 CWE-307

References

Other 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 https://github.com/hotspotbilling/phpnuxbill/security/advisories/GHSA-337r-rrrc-r559

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-108109? +

CVE-2026-108109 has a CVSS v3.1 score of 9.1 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0039, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-108109? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-108109