{"id":"CVE-2025-55702","kind":"vulnerability","aliases":["CVE-2025-55702"],"related":[],"title":"Apache Traffic Server: Expect 100-continue request smuggling past front-end proxies","description":"When a client sends a POST with Expect: 100-continue and the origin answers before reading the body, Apache Traffic Server parses the unread body left on the client connection as the next request. An attacker behind a front-end proxy that shares connections to Traffic Server can use this to smuggle requests past the front end and desynchronize responses for other users.\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 parses an unread POST body left on a client connection as a new request when the origin answers early to an Expect: 100-continue request. An attacker behind a front-end proxy that shares connections with Traffic Server can smuggle requests past the front end and desynchronize responses for other users.","severity":"high","cvss":8.7,"epss":0.00253,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["apache-traffic-server","reverse-proxy","runtime","self-hosted"],"not_affected_if":["default-config"],"how_to_check":"Check the installed Traffic Server version (for example with traffic_server -V) and see whether it falls in 8.0.0-8.1.11, 9.0.0-9.2.15, 10.0.0-10.1.4, or 10.2.0.","fix":"Upgrade to 9.2.16, 10.1.5, or 10.2.1, per the advisory.","status":"open","published_at":"2026-10-21T19:16:48+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","triaged_at":"2026-10-23T22:36:53+00:00","updated_at":"2026-10-24T13:15:54+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-10-23T22:36:53Z","model":"claude-haiku-5-5","output":{"fix":"Upgrade to 9.2.16, 10.1.5, or 10.2.1, per the advisory.","reach":"network","title":"Apache Traffic Server: Expect 100-continue request smuggling past front-end proxies","impact":"high","summary":"Apache Traffic Server parses an unread POST body left on a client connection as a new request when the origin answers early to an Expect: 100-continue request. An attacker behind a front-end proxy that shares connections with Traffic Server can smuggle requests past the front end and desynchronize responses for other users.","category":"runtime","who_cares":["apache-traffic-server","reverse-proxy","self-hosted"],"confidence":0.7,"needs_auth":"unknown","worst_case":"Attackers smuggle requests and poison responses served to other users.","analyst_note":"","how_to_check":"Check the installed Traffic Server version (for example with traffic_server -V) and see whether it falls in 8.0.0-8.1.11, 9.0.0-9.2.15, 10.0.0-10.1.4, or 10.2.0.\nunknown","needs_analyst":false,"not_affected_if":["default-config"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.00052,"input_tokens":3032,"output_tokens":434,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2025':15A,18A '-55702':16A,19A '10.0.0':165C '10.1.4':167C '10.1.5':177C '10.2.0':168C '10.2.1':179C '100':5A,56B,94C '8.0.0':157C '8.1.11':159C '9.0.0':161C '9.2.15':163C '9.2.16':176C 'affect':152C 'answer':51B,99C 'apach':1A,21B,31B,104C,153C 'apache-traffic-serv':20B 'attack':60B,121C 'behind':61B,122C 'bodi':38B,103C,110C 'client':42B,88C,114C 'connect':43B,69B,115C,130C 'continu':6A,57B,95C 'cve':14A,17A 'desynchron':81B,145C 'earli':52B 'end':12A,65B,79B,126C,143C 'expect':4A,55B,93C 'fix':181C 'front':11A,64B,78B,125C,142C 'front-end':10A,63B,124C 'host':30B 'issu':151C,183C 'left':39B,111C 'new':46B 'next':118C 'origin':50B,98C 'pars':34B,107C 'past':9A,76B,140C 'post':37B,91C 'proxi':13A,26B,66B,127C 'read':101C 'recommend':171C 'request':7A,47B,58B,75B,119C,139C 'respons':82B,146C 'revers':25B 'reverse-proxi':24B 'runtim':27B 'self':29B 'self-host':28B 'send':89C 'server':3A,23B,33B,72B,106C,133C,155C 'share':68B,129C 'smuggl':8A,74B,138C 'traffic':2A,22B,32B,71B,105C,132C,154C 'unread':36B,109C 'upgrad':173C 'use':135C 'user':85B,149C,169C 'version':175C","nicknames":[],"mitigations":[],"who_affected":null,"tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T19:16:48+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/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-2025-55702","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-55702","severity":null,"published_at":"2026-10-21T19:16:48+00:00","modified_at":"2026-10-23T12:18:05+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-2025-55702","url":"https://api.first.org/data/v1/epss?cve=CVE-2025-55702","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"}