{"id":"CVE-2026-42020","kind":"vulnerability","aliases":["CVE-2026-42020"],"related":[],"title":"Totolink X2000R router: stack overflow in IPv6 PPPoE setup lets attackers run code","description":"Multiple stack-based buffer overflow vulnerabilities exist in the boa formIpv6Setup pppoe functionality of Totolink X2000R TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327. A specially crafted HTTP request can lead to arbitrary code execution. An attacker can make an authenticated HTTP request to trigger these vulnerabilities. This vulnerability concerns the pppoe_dns2 parameter.","summary":"Stack buffer overflows in the boa web server's formIpv6Setup PPPoE handler (pppoe_dns2 parameter) on Totolink X2000R firmware B20250421.1327 allow code execution via a crafted HTTP request. Requires admin login (CVSS 9.1, PR:H); no fix or public exploit known.","severity":"critical","cvss":9.1,"epss":null,"exploited":false,"exploited_at":null,"products":[{"name":"Totolink X2000R firmware","fixed":[],"affected":"TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327","ecosystem":"firmware"}],"ecosystems":[],"tags":["infrastructure","router","self-hosted","totolink","x2000r"],"not_affected_if":["auth-required","remote-management-disabled"],"how_to_check":"In the router web UI (System/Status page) read the firmware version; affected if it is TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327. Also check whether the admin web interface (boa) is reachable from WAN.","fix":"No fixed firmware published as of 2026-10-23 (unknown). Check TOTOLINK's download page for X2000R. Mitigate: disable WAN/remote management, restrict the admin UI to a trusted LAN, change the default admin password, and avoid IPv6 PPPoE setup from untrusted users.","status":"open","published_at":"2026-10-20T21:17:19+00:00","first_seen_at":"2026-10-23T21:57:21+00:00","triaged_at":"2026-10-23T22:39:08+00:00","updated_at":"2026-10-23T23:13:36+00:00","category":"infrastructure","confidence":0.7,"triage":{"at":"2026-10-23T22:39:08Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Totolink X2000R router: stack overflow in IPv6 PPPoE setup lets attackers run code","impact":"high","summary":"The web management server (boa) on Totolink X2000R routers has stack buffer overflows in its IPv6 PPPoE setup handler, triggered through the pppoe_dns2 parameter. An attacker who can log in to the router's web interface can send a crafted HTTP request to execute code on the device.","category":"infrastructure","who_cares":["totolink","x2000r","router","self-hosted"],"confidence":0.8,"needs_auth":"yes","worst_case":"attacker runs code on the router as the device admin","analyst_note":"Check the vendor or NVD advisory for a fixed firmware build and the admin-interface exposure; the sources give no fixed version.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["auth-required"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"critical"},"cost_usd":0.000481,"input_tokens":3002,"output_tokens":361,"severity_before":"critical"},"analyst_status":"done","analyst_note":"Check the vendor or NVD advisory for a fixed firmware build and the admin-interface exposure; the sources give no fixed version.","search":"'-2026':15A,18A '-42020':16A,19A '0.0':93C '9.1':62B 'admin':59B 'allow':50B 'arbitrari':103C 'attack':11A,107C 'authent':111C 'b20250421.1327':49B,94C 'base':74C 'boa':35B,81C 'buffer':31B,75C 'code':13A,51B,104C 'concern':120C 'craft':55B,97C 'cve':14A,17A 'cvss':61B 'dns2':43B,123C 'execut':52B,105C 'exist':78C 'exploit':69B 'firmwar':48B 'firmware':22A 'fix':66B 'formipv6setup':39B,82C 'function':84C 'gh':91C 'h':64B 'handler':41B 'host':27B 'http':56B,98C,112C 'infrastructur':23B 'ipv6':7A 'known':70B 'lead':101C 'let':10A 'login':60B 'make':109C 'multipl':71C 'overflow':5A,32B,76C 'paramet':44B,124C 'pppoe':8A,40B,42B,83C,122C 'pr':63B 'public':68B 'request':57B,99C,113C 'requir':58B 'router':3A,24B 'run':12A 'self':26B 'self-host':25B 'server':37B 'setup':9A 'special':96C 'stack':4A,30B,73C 'stack-bas':72C 'totolink':1A,20A,28B,46B,86C,89C 'totolink-x2000r-gh-v1':88C 'trigger':115C 'v1':92C 'via':53B 'vulner':77C,117C,119C 'web':36B 'x2000r':2A,21A,29B,47B,87C,90C","nicknames":[],"mitigations":[],"who_affected":null,"tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-20T21:17:19+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H","cvss_by":"talos-cna@cisco.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-42020","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42020","severity":null,"published_at":"2026-10-20T21:17:19+00:00","modified_at":"2026-10-22T15:31:24+00:00","first_seen_at":"2026-10-23T21:57:21+00:00","fetched_at":"2026-10-23T22:28:58+00:00","note":null},{"source":"analyst","external_id":"CVE-2026-42020:396","url":null,"severity":null,"published_at":"2026-10-23T23:13:36+00:00","modified_at":"2026-10-23T23:13:36+00:00","first_seen_at":"2026-10-23T23:13:36+00:00","fetched_at":"2026-10-23T23:13:36+00:00","note":"CVE.org record and VulDB read: only build TOTOLINK-X2000R-Gh-V1.0.0-B20250421.1327 listed; no vendor advisory, no fixed firmware, no public exploit, not in KEV, no social discussion checked."}],"documents":[{"id":1848,"url":"https://www.cve.org/CVERecord?id=CVE-2026-42020","title":"CVE Record: CVE-2026-42020","kind":"advisory","source":"analyst","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":null},{"id":1846,"url":"https://vuldb.com/vuln/424068","title":"VulDB: Totolink X2000R formIpv6Setup pppoe_dns2 buffer overflow","kind":"other","source":"analyst","text":null,"published_at":null,"relation":"mentions","confidence":null,"note":null}],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}