{"id":"CVE-2026-112374","kind":"vulnerability","aliases":["CVE-2026-112374"],"related":[],"title":"FOSSBilling: staff login form lets attackers force a victim's browser login","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.","summary":"FOSSBilling before 0.8.9 accepts staff login requests at POST /api/guest/staff/login without CSRF or Origin checks. A malicious page can auto-submit a form that silently logs a visitor's browser into an attacker-controlled staff account.","severity":"medium","cvss":5.1,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["fossbilling","package","php","self-hosted"],"not_affected_if":["fossbilling-0.8.9-or-later"],"how_to_check":"- Check the installed FOSSBilling version and confirm it is below `0.8.9`.\n- Look for the route `/api/guest/staff/login` in the deployed code or web server logs.","fix":"- Move FOSSBilling to `0.8.9` or later, per the NVD description.","status":"open","published_at":"2026-10-30T13:18:29+00:00","first_seen_at":"2026-10-30T13:30:27+00:00","triaged_at":"2026-10-30T13:32:15+00:00","updated_at":"2026-10-30T13:32:15+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-30T13:32:15Z","model":"claude-haiku-5-5","output":{"fix":"- Move FOSSBilling to `0.8.9` or later, per the NVD description.","reach":"internet","title":"FOSSBilling: staff login form lets attackers force a victim's browser login","impact":"medium","summary":"FOSSBilling before 0.8.9 accepts staff login requests at POST /api/guest/staff/login without CSRF or Origin checks. A malicious page can auto-submit a form that silently logs a visitor's browser into an attacker-controlled staff account.","audience":"businesses","category":"package","nicknames":[],"who_cares":["fossbilling","self-hosted","php"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"victim browser logged into attacker's staff account silently","analyst_note":"","how_to_check":"- Check the installed FOSSBilling version and confirm it is below `0.8.9`.\n- Look for the route `/api/guest/staff/login` in the deployed code or web server logs.","plain_action":"","needs_analyst":false,"not_affected_if":["fossbilling-0.8.9-or-later"],"who_is_affected":"Any FOSSBilling installation older than 0.8.9 that exposes its staff login endpoint to the internet. The risk is a staff member's browser being logged into an attacker's account after they visit a malicious page. Instances where the staff login endpoint is not reachable from the internet are less exposed.","user_interaction":"yes","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000682,"input_tokens":4205,"output_tokens":523,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-112374':15A,18A '-2026':14A,17A '/api/guest/staff/login':34B,81C '0.8.9':27B,65C 'accept':28B 'account':62B,132C 'allow':83C 'allowlist':92C 'attack':6A,59B,85C,106C,117C,129C 'attacker-control':58B,116C 'authent':88C 'auto':45B,111C 'auto-submit':44B,110C 'browser':11A,55B,126C 'check':39B 'checkguestclientauthent':90C 'client':93C,96C 'contain':66C 'control':60B,118C 'creat':97C 'credenti':119C 'cross':69C 'cross-sit':68C 'csrf':36B,102C 'cve':13A,16A 'endpoint':79C 'forc':7A,87C 'forgeri':72C 'form':4A,48B,114C 'fossbil':1A,19B,25B,63C 'guest':77C 'host':24B,108C 'html':113C 'leav':98C 'let':5A 'log':51B,122C 'login':3A,12A,30B,78C,94C,100C 'malici':41B 'origin':38B,104C 'packag':20B 'page':42B 'php':21B 'post':33B,80C 'remot':84C 'request':31B,71C 'self':23B 'self-host':22B 'silent':50B,121C 'site':70C 'staff':2A,29B,61B,76C,99C,131C 'submit':46B,112C 'valid':105C 'victim':9A,124C 'visitor':53B 'vulner':73C 'without':35B,101C","nicknames":[],"mitigations":[],"who_affected":"Any FOSSBilling installation older than 0.8.9 that exposes its staff login endpoint to the internet. The risk is a staff member's browser being logged into an attacker's account after they visit a malicious page. Instances where the staff login endpoint is not reachable from the internet are less exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"first_public_at":"2026-10-30T13:18:29+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-112374","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-112374","severity":null,"published_at":"2026-10-30T13:18:29+00:00","modified_at":"2026-10-30T13:18:29+00:00","first_seen_at":"2026-10-30T13:30:27+00:00","fetched_at":"2026-10-30T13:30:27+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}