{"id":"CVE-2021-20090","kind":"vulnerability","aliases":["CVE-2021-20090"],"related":[],"title":"Arcadyan Buffalo Firmware: Arcadyan Buffalo Firmware Path Traversal Vulnerability","description":"Arcadyan Buffalo firmware contains a path traversal vulnerability that could allow unauthenticated, remote attackers to bypass authentication and access sensitive information. This vulnerability affects multiple routers across several different vendors.\n\nCISA required action: Apply updates per vendor instructions.","summary":"Arcadyan Buffalo router firmware has a path traversal flaw that lets remote attackers bypass authentication and read sensitive information. CISA lists it as actively exploited in the wild.","severity":"critical","cvss":9.8,"epss":0.99982,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Arcadyan Buffalo Firmware","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["arcadyan","buffalo","exploited","infrastructure","routers","self-hosted"],"not_affected_if":["unknown"],"how_to_check":null,"fix":"Apply firmware updates per vendor instructions, as CISA directs; the specific fixed versions are unknown from the sources.","status":"open","published_at":"2021-04-29T15:15:10+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:33:56+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:33:56Z","model":"claude-haiku-5-5","output":{"fix":"Apply firmware updates per vendor instructions, as CISA directs; the specific fixed versions are unknown from the sources.","reach":"internet","impact":"medium","summary":"Arcadyan Buffalo router firmware has a path traversal flaw that lets remote attackers bypass authentication and read sensitive information. CISA lists it as actively exploited in the wild.","category":"infrastructure","who_cares":["routers","buffalo","arcadyan","self-hosted"],"confidence":0.6,"needs_auth":"no","worst_case":"Remote unauthenticated attacker reads sensitive device information, bypassing authentication","analyst_note":"Find the affected device models and fixed firmware versions from the vendor advisories and the CISA KEV entry; sources give no versions.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["unknown"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000458,"input_tokens":2874,"output_tokens":342,"severity_before":"unknown"},"analyst_status":"queued","analyst_note":"Find the affected device models and fixed firmware versions from the vendor advisories and the CISA KEV entry; sources give no versions.","search":"'-20090':12A,15A '-2021':11A,14A 'access':73C 'across':81C 'action':87C 'activ':50B 'affect':78C 'allow':65C 'appli':88C 'arcadyan':1A,4A,16A,19B,27B,55C 'attack':39B,68C 'authent':41B,71C 'buffalo':2A,5A,17A,20B,28B,56C 'bypass':40B,70C 'cisa':46B,85C 'contain':58C 'could':64C 'cve':10A,13A 'differ':83C 'exploit':21B,51B 'firmwar':3A,6A,30B,57C 'firmware':18A 'flaw':35B 'host':26B 'inform':45B,75C 'infrastructur':22B 'instruct':92C 'let':37B 'list':47B 'multipl':79C 'path':7A,33B,60C 'per':90C 'read':43B 'remot':38B,67C 'requir':86C 'router':23B,29B,80C 'self':25B 'self-host':24B 'sensit':44B,74C 'sever':82C 'travers':8A,34B,61C 'unauthent':66C 'updat':89C 'vendor':84C,91C 'vulner':9A,62C,77C 'wild':54B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-04-29T15:15:10+00:00","kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvss_by":"nvd@nist.gov","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-20090","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-20090","severity":null,"published_at":"2021-11-03T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:53+00:00","fetched_at":"2026-10-25T16:39:49+00:00","note":null},{"source":"epss","external_id":"CVE-2021-20090","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-20090","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:44+00:00","fetched_at":"2026-10-23T19:13:44+00:00","note":null},{"source":"nvd","external_id":"CVE-2021-20090","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-20090","severity":null,"published_at":"2021-04-29T15:15:10+00:00","modified_at":"2026-06-17T03:33:15+00:00","first_seen_at":"2026-10-23T21:57:35+00:00","fetched_at":"2026-10-23T21:57:35+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"}