{"id":"CVE-2026-20179","kind":"vulnerability","aliases":["CVE-2026-20179"],"related":[],"title":"Cisco Snort 3: crafted GRE packet crashes intrusion detection engine","description":"Multiple Cisco products are affected by a vulnerability in the Snort 3 Generic Routing Encapsulation (GRE) Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection.\r\n\r\nThis vulnerability is due to incomplete error checking when Snort 3 parses GRE packets. An attacker could exploit this vulnerability by sending a crafted GRE packet to a targeted device to be parsed by Snort. A successful exploit could allow the attacker to cause the Snort 3 Detection Engine to restart unexpectedly, resulting in a DoS condition.","summary":"Several Cisco products run a Snort 3 engine that inspects GRE-encapsulated traffic and fails to check errors while parsing it. A remote, unauthenticated attacker who sends a crafted GRE packet can restart the Snort 3 detection engine, interrupting packet inspection (denial of service).","severity":"medium","cvss":5.8,"epss":0.0039,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["cisco","firewall","infrastructure","network-security","snort-3"],"not_affected_if":["no-snort-3"],"how_to_check":"- unknown","fix":"- unknown","status":"open","published_at":"2026-10-21T17:18:27+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","triaged_at":"2026-10-25T04:10:03+00:00","updated_at":"2026-10-25T04:10:03+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-25T04:10:03Z","model":"claude-haiku-5-5","output":{"fix":"- unknown","reach":"network","title":"Cisco Snort 3: crafted GRE packet crashes intrusion detection engine","impact":"low","summary":"Several Cisco products run a Snort 3 engine that inspects GRE-encapsulated traffic and fails to check errors while parsing it. A remote, unauthenticated attacker who sends a crafted GRE packet can restart the Snort 3 detection engine, interrupting packet inspection (denial of service).","category":"infrastructure","nicknames":[],"who_cares":["cisco","snort-3","network-security","firewall"],"confidence":0.6,"needs_auth":"no","worst_case":"Snort 3 detection engine restarts, interrupting packet inspection until recovery","analyst_note":"Find the list of affected Cisco products and fixed versions in the Cisco security advisory for CVE-2026-20179; the sources given do not name them.","how_to_check":"- unknown","needs_analyst":true,"not_affected_if":["no-snort-3"],"who_is_affected":"Organizations running Cisco products that include the Snort 3 detection engine with GRE inspection enabled are exposed to a restart of the inspection engine. The sources do not list the affected product versions or confirm which deployments inspect GRE traffic by default. Teams that do not run Cisco Snort 3 inspection can skip it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000601,"input_tokens":3494,"output_tokens":503,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-20179':13A,16A '-2026':12A,15A '-3':24B '3':3A,31B,61B,81C,99C,121C,157C 'affect':74C 'allow':90C,150C 'attack':50B,94C,126C,152C 'caus':96C,154C 'check':42B,118C 'cisco':1A,17B,26B,71C 'condit':167C 'could':89C,127C,149C 'craft':4A,54B,134C 'crash':7A 'cve':11A,14A 'denial':67B 'detect':9A,62B,86C,100C,158C 'devic':140C 'dos':166C 'due':114C 'encapsul':37B,84C 'engin':10A,32B,63B,87C,101C,159C 'error':43B,117C 'exploit':128C,148C 'fail':40B 'firewal':18B 'generic':82C 'gre':5A,36B,55B,85C,123C,135C 'gre-encapsul':35B 'incomplet':116C 'infrastructur':19B 'inspect':34B,66B,110C 'interrupt':64B,107C 'intrus':8A 'multipl':70C 'network':21B 'network-secur':20B 'packet':6A,56B,65B,109C,124C,136C 'pars':45B,122C,143C 'product':27B,72C 'remot':48B,93C 'restart':58B,103C,161C 'result':104C,163C 'rout':83C 'run':28B 'secur':22B 'send':52B,132C 'servic':69B 'sever':25B 'snort':2A,23B,30B,60B,80C,98C,120C,145C,156C 'success':147C 'target':139C 'traffic':38B 'unauthent':49B,92C 'unexpect':162C 'vulner':77C,112C,130C","nicknames":[],"mitigations":[],"who_affected":"Organizations running Cisco products that include the Snort 3 detection engine with GRE inspection enabled are exposed to a restart of the inspection engine. The sources do not list the affected product versions or confirm which deployments inspect GRE traffic by default. Teams that do not run Cisco Snort 3 inspection can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T17:18:27+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","cvss_by":"psirt@cisco.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-20179","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-20179","severity":null,"published_at":"2026-10-21T17:18:27+00:00","modified_at":"2026-10-22T14:17:40+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","fetched_at":"2026-10-23T22:29:01+00:00","note":null},{"source":"epss","external_id":"CVE-2026-20179","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-20179","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T13:15:54+00:00","fetched_at":"2026-10-24T13:15:54+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"}