{"id":"CVE-2026-111809","kind":"vulnerability","aliases":["CVE-2026-111809"],"related":[],"title":"Apache Traffic Server: HEAD requests enable request smuggling past proxies","description":"Apache Traffic Server allows request smuggling via HEAD requests that carry Content-Length or Transfer-Encoding.\n\n\n\nThis issue affects Apache Traffic Server: from 8.0.0 through 8.1.11, from 9.0.0 through 9.2.15, from 10.0.0 through 10.1.4, 10.2.0.\n\n\n\nUsers are recommended to upgrade to version 9.2.16, 10.1.5, or 10.2.1, which fix the issue.","summary":"Apache Traffic Server mishandles HEAD requests that carry Content-Length or Transfer-Encoding headers, letting a remote attacker desynchronize request parsing. An attacker can smuggle requests through the proxy to reach back-end handling that should be blocked.","severity":"critical","cvss":9.3,"epss":0.00218,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["apache-traffic-server","infrastructure","runtime","self-hosted"],"not_affected_if":["managed-hosting"],"how_to_check":"Check the running version, for example with traffic_server -V or the installed package version; affected are 8.0.0 to 8.1.11, 9.0.0 to 9.2.15, 10.0.0 to 10.1.4, and 10.2.0.","fix":"Upgrade to 9.2.16, 10.1.5, or 10.2.1, matching your major line.","status":"open","published_at":"2026-10-21T20:17:22+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","triaged_at":"2026-10-23T22:32:53+00:00","updated_at":"2026-10-24T13:15:54+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-10-23T22:32:53Z","model":"claude-haiku-5-5","output":{"fix":"Upgrade to 9.2.16, 10.1.5, or 10.2.1, matching your major line.\nunknown","reach":"internet","title":"Apache Traffic Server: HEAD requests enable request smuggling past proxies","impact":"high","summary":"Apache Traffic Server mishandles HEAD requests that carry Content-Length or Transfer-Encoding headers, letting a remote attacker desynchronize request parsing. An attacker can smuggle requests through the proxy to reach back-end handling that should be blocked.","category":"runtime","who_cares":["apache-traffic-server","self-hosted"],"confidence":0.7,"needs_auth":"no","worst_case":"Attacker smuggles requests past the proxy to back-end servers","analyst_note":"Confirm the exact smuggling impact and whether the cvss 9.3 vector is network-reachable with no auth; check the Apache Traffic Server security advisory for workarounds.","how_to_check":"Check the running version, for example with traffic_server -V or the installed package version; affected are 8.0.0 to 8.1.11, 9.0.0 to 9.2.15, 10.0.0 to 10.1.4, and 10.2.0.","needs_analyst":true,"not_affected_if":["managed-hosting"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"critical"},"cost_usd":0.000538,"input_tokens":2990,"output_tokens":478,"severity_before":"critical"},"analyst_status":null,"analyst_note":null,"search":"'-111809':13A,16A '-2026':12A,15A '10.0.0':100C '10.1.4':102C '10.1.5':112C '10.2.0':103C '10.2.1':114C '8.0.0':92C '8.1.11':94C '9.0.0':96C '9.2.15':98C '9.2.16':111C 'affect':87C 'allow':70C 'apach':1A,18B,26B,67C,88C 'apache-traffic-serv':17B 'attack':45B,50B 'back':60B 'back-end':59B 'block':66B 'carri':33B,77C 'content':35B,79C 'content-length':34B,78C 'cve':11A,14A 'desynchron':46B 'enabl':6A 'encod':40B,84C 'end':61B 'fix':116C 'handl':62B 'head':4A,30B,74C 'header':41B 'host':25B 'infrastructur':21B 'issu':86C,118C 'length':36B,80C 'let':42B 'mishandl':29B 'pars':48B 'past':9A 'proxi':10A,56B 'reach':58B 'recommend':106C 'remot':44B 'request':5A,7A,31B,47B,53B,71C,75C 'runtim':22B 'self':24B 'self-host':23B 'server':3A,20B,28B,69C,90C 'smuggl':8A,52B,72C 'traffic':2A,19B,27B,68C,89C 'transfer':39B,83C 'transfer-encod':38B,82C 'upgrad':108C 'user':104C 'version':110C 'via':73C","nicknames":[],"mitigations":[],"who_affected":null,"tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T20:17:22+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:H/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":"security@apache.org","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-111809","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-111809","severity":null,"published_at":"2026-10-21T20:17:22+00:00","modified_at":"2026-10-22T16:56:52+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","fetched_at":"2026-10-23T22:29:02+00:00","note":null},{"source":"epss","external_id":"CVE-2026-111809","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-111809","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"}