{"id":"CVE-2026-119425","kind":"vulnerability","aliases":["CVE-2026-119425"],"related":[],"title":"OPNsense: captive portal roaming flaw lets attackers hijack logged-in client sessions","description":"OPNsense core 26.1.6 through 26.7.7 contains an authentication bypass vulnerability in the captive portal roaming feature that lets unauthenticated attackers hijack authorized client sessions by spoofing unauthenticated MAC-to-IP observations. Attackers on the same Layer-2 segment can send forged gratuitous ARP replies binding their IP to a victim's MAC, gaining portal access with traffic attributed to the victim.","summary":"OPNsense's captive portal roaming feature trusts unauthenticated MAC-to-IP observations, so a device can be spoofed. An attacker on the same Layer-2 network can send forged ARP replies to take over an authorized user's portal session and its traffic attribution.","severity":"medium","cvss":5.4,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["captive-portal","firewall","infrastructure","opnsense","self-hosted"],"not_affected_if":["captive-portal-not-used","outside-version-range","roaming-disabled"],"how_to_check":"- Check the installed OPNsense version in the web UI or with `opnsense-version`\n- Confirm whether the captive portal roaming feature is enabled in the portal settings","fix":"- OPNsense core: move to a release newer than `26.7.7`; the sources do not name the fixed version","status":"open","published_at":"2026-10-30T12:16:39+00:00","first_seen_at":"2026-10-30T12:30:25+00:00","triaged_at":"2026-10-30T12:32:53+00:00","updated_at":"2026-10-30T12:32:53+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-30T12:32:53Z","model":"claude-haiku-5-5","output":{"fix":"- OPNsense core: move to a release newer than `26.7.7`; the sources do not name the fixed version","reach":"local","title":"OPNsense: captive portal roaming flaw lets attackers hijack logged-in client sessions","impact":"medium","summary":"OPNsense's captive portal roaming feature trusts unauthenticated MAC-to-IP observations, so a device can be spoofed. An attacker on the same Layer-2 network can send forged ARP replies to take over an authorized user's portal session and its traffic attribution.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["opnsense","captive-portal","firewall","self-hosted"],"confidence":0.6,"fix_status":"unknown","needs_auth":"no","worst_case":"attacker takes over another user's authorized portal session","analyst_note":"Confirm the fixed OPNsense version and any roaming-feature setting change from the NVD entry or the OPNsense advisory.","how_to_check":"- Check the installed OPNsense version in the web UI or with `opnsense-version`\n- Confirm whether the captive portal roaming feature is enabled in the portal settings\n- unknown for other checks; the sources do not say","plain_action":"","needs_analyst":true,"not_affected_if":["captive-portal-not-used","roaming-disabled","outside-version-range"],"who_is_affected":"Networks running OPNsense 26.1.6 through 26.7.7 with the captive portal in use, especially where the roaming feature is on. Attackers need to be on the same Layer-2 segment as the users, so exposure is limited to the local network. Installations without the captive portal, or on versions outside that range, can skip it.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"medium"},"cost_usd":0.000728,"input_tokens":4184,"output_tokens":620,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-119425':16A,19A '-2':54B,111C '-2026':15A,18A '26.1.6':76C '26.7.7':78C 'access':129C 'arp':59B,117C 'attack':7A,49B,93C,106C 'attribut':73B,132C 'authent':81C 'author':65B,95C 'bind':119C 'bypass':82C 'captiv':2A,21B,31B,86C 'captive-port':20B 'client':12A,96C 'contain':79C 'core':75C 'cve':14A,17A 'devic':44B 'featur':34B,89C 'firewal':23B 'flaw':5A 'forg':58B,115C 'gain':127C 'gratuit':116C 'hijack':8A,94C 'host':28B 'infrastructur':24B 'ip':40B,104C,121C 'layer':53B,110C 'let':6A,91C 'log':10A 'logged-in':9A 'mac':38B,102C,126C 'mac-to-ip':37B,101C 'network':55B 'observ':41B,105C 'opnsens':1A,25B,29B,74C 'portal':3A,22B,32B,68B,87C,128C 'repli':60B,118C 'roam':4A,33B,88C 'segment':112C 'self':27B 'self-host':26B 'send':57B,114C 'session':13A,69B,97C 'spoof':47B,99C 'take':62B 'traffic':72B,131C 'trust':35B 'unauthent':36B,92C,100C 'user':66B 'victim':124C,135C 'vulner':83C","nicknames":[],"mitigations":[],"who_affected":"Networks running OPNsense 26.1.6 through 26.7.7 with the captive portal in use, especially where the roaming feature is on. Attackers need to be on the same Layer-2 segment as the users, so exposure is limited to the local network. Installations without the captive portal, or on versions outside that range, can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"unknown","audience":"businesses","plain_action":null,"first_public_at":"2026-10-30T12:16:39+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/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-2026-119425","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-119425","severity":null,"published_at":"2026-10-30T12:16:39+00:00","modified_at":"2026-10-30T12:16:39+00:00","first_seen_at":"2026-10-30T12:30:25+00:00","fetched_at":"2026-10-30T12:30:25+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"}