---
id: CVE-2026-112374
title: FOSSBilling before 0.8.9 Login CSRF via Staff Guest Login API
summary: >-
  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() on…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N'
cvssSource: cna
cwe:
  - CWE-352
vendor: FOSSBilling
product: FOSSBilling
affected:
  - FOSSBilling >= 0.1.0 < 0.8.9
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T21:23:53.494731Z'
published: '2026-10-30'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T21:24:07.055Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-112374'
references:
  - url: >-
      https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-h7w3-wp25-gf86
    label: Vendor Advisory
  - url: 'https://github.com/FOSSBilling/FOSSBilling/releases/tag/0.8.9'
    label: Vendor Patch
  - url: >-
      https://www.vulncheck.com/advisories/fossbilling-before-login-csrf-via-staff-guest-login-api
    label: >-
      VulnCheck Advisory: FOSSBilling before 0.8.9 Login CSRF via Staff Guest
      Login API
tags:
  - cve.org
epss: 0.00172
epssPercentile: 0.06662
ingestedAt: '2026-11-03T11:43:15.777Z'
---

## Overview

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

- `FOSSBilling >= 0.1.0 < 0.8.9`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.