Vulnerability · Published Oct 30, 2026 · Assigned by VulnCheck

CVE-2026-112374FOSSBilling before 0.8.9 Login CSRF via Staff Guest Login API

Medium 4.3

In plain English

A medium-severity cross-site request forgery in FOSSBilling from FOSSBilling. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities).

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.2%top 93.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

FOSSBilling before 0.8.9 contains a Cross-Site Request Forgery vulnerability in the staff guest login endpoint (POST /api/guest/staff/login) that allows remote attackers to force authentication because checkGuestClientAuthentication() only allowlists client_login and client_create, leaving staff_login without CSRF or Origin validation. Attackers can host an auto-submitting HTML form with attacker-controlled credentials to silently log a victim's browser into the attacker's staff account.

Affected products (as reported)

Vendor	Product	Versions
FOSSBilling	FOSSBilling	0.1.0 – before 0.8.9

Weakness: CWE-352 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

References

Vendor Advisory vendor-advisory, technical-description
Vendor Patch patch, issue-tracking
VulnCheck Advisory: FOSSBilling before 0.8.9 Login CSRF via Staff Guest Login API third-party-advisory