{"id":"CVE-2026-20011","kind":"vulnerability","aliases":["CVE-2026-20011"],"related":[],"title":"Cisco Snort 3: crafted SMTP MIME headers crash the detection engine","description":"Multiple Cisco products are affected by a vulnerability in the Snort 3 SMTP MIME Decoder that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart.\r\n\r\nThis vulnerability is due to a lack of error checking when the MIME fields of the SMTP header are parsed. An attacker could exploit this vulnerability by sending crafted SMTP packets through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when the Snort 3 Detection Engine unexpectedly restarts.","summary":"Snort 3 in multiple Cisco products fails to check errors while parsing MIME fields in SMTP headers. A remote, unauthenticated attacker can send crafted SMTP traffic to make the Snort 3 Detection Engine restart, causing denial of service.","severity":"medium","cvss":5.8,"epss":0.00416,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["cisco","infrastructure","network-security","smtp","snort"],"not_affected_if":["snort-not-deployed"],"how_to_check":null,"fix":null,"status":"open","published_at":"2026-10-21T17:18:26+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","triaged_at":"2026-10-25T04:10:05+00:00","updated_at":"2026-10-25T04:10:05+00:00","category":"infrastructure","confidence":0.7,"triage":{"at":"2026-10-25T04:10:05Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Cisco Snort 3: crafted SMTP MIME headers crash the detection engine","impact":"low","summary":"Snort 3 in multiple Cisco products fails to check errors while parsing MIME fields in SMTP headers. A remote, unauthenticated attacker can send crafted SMTP traffic to make the Snort 3 Detection Engine restart, causing denial of service.","category":"infrastructure","nicknames":[],"who_cares":["cisco","snort","network-security","smtp"],"confidence":0.7,"needs_auth":"no","worst_case":"Snort 3 detection engine restarts, interrupting traffic inspection","analyst_note":"Fetch the Cisco advisory for the affected product list, fixed versions and workarounds; the NVD entry gives no versions.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["snort-not-deployed"],"who_is_affected":"Affected products are Cisco products that ship Snort 3 with SMTP inspection enabled, as named in the Cisco advisory. Sources do not list the exact product or version set, so check the vendor advisory before deciding. Systems that do not run Snort 3 SMTP inspection are likely not affected.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000583,"input_tokens":3470,"output_tokens":471,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-20011':14A,17A '-2026':13A,16A '3':3A,26B,55B,74C,89C,134C,153C 'affect':67C 'allow':80C,139C 'attack':45B,84C,115C,141C 'caus':59B,86C,143C 'check':33B,103C 'cisco':1A,18B,29B,64C 'condit':149C 'connect':128C 'could':79C,116C,138C 'craft':4A,48B,122C 'crash':8A 'cve':12A,15A 'decod':77C 'denial':60B,145C 'detect':10A,56B,90C,154C 'dos':148C 'due':97C 'engin':11A,57B,91C,155C 'error':34B,102C 'establish':127C 'exploit':117C,137C 'fail':31B 'field':38B,107C 'header':7A,41B,111C 'infrastructur':19B 'lack':100C 'make':52B 'mime':6A,37B,76C,106C 'multipl':28B,63C 'network':21B 'network-secur':20B 'packet':124C 'pars':36B,113C,131C 'product':30B,65C 'remot':43B,83C 'restart':58B,93C,157C 'secur':22B 'send':47B,121C 'servic':62B,147C 'smtp':5A,23B,40B,49B,75C,110C,123C 'snort':2A,24B,25B,54B,73C,88C,133C,152C 'success':136C 'traffic':50B 'unauthent':44B,82C 'unexpect':156C 'vulner':70C,95C,119C","nicknames":[],"mitigations":[],"who_affected":"Affected products are Cisco products that ship Snort 3 with SMTP inspection enabled, as named in the Cisco advisory. Sources do not list the exact product or version set, so check the vendor advisory before deciding. Systems that do not run Snort 3 SMTP inspection are likely not affected.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T17:18:26+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-2026-20011","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-20011","severity":null,"published_at":"2026-10-21T17:18:26+00:00","modified_at":"2026-10-22T14:17:39+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-2026-20011","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-20011","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"}