{"id":"CVE-2026-114656","kind":"vulnerability","aliases":["CVE-2026-114656"],"related":[],"title":"Traefik: negated Host rules let clients skip client-certificate checks","description":"Traefik before 2.11.58 and 3.7.13 contains an authentication bypass vulnerability that allows unauthenticated clients to skip client-certificate checks because negated Host matchers are counted as served domains. Attackers can reach backends protected by RequireAndVerifyClientCert when a router rule with !Host() creates a TLS options conflict that falls back to the default options.","summary":"Traefik before 2.11.58 and 3.7.13 counts negated Host matchers as served domains, which can create a TLS options conflict that falls back to default options. An unauthenticated client can then reach backends that were meant to require verified client certificates.","severity":"high","cvss":7.5,"epss":0.00163,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["infrastructure","kubernetes","mtls","self-hosted","traefik"],"not_affected_if":["no-client-cert-auth","no-negated-host-rules","patched-version"],"how_to_check":"- Run `traefik version` (or check the container image tag) and compare against `2.11.58` and `3.7.13`\n- Look for routers using `!Host(` rules alongside `RequireAndVerifyClientCert` TLS options in the dynamic configuration\n- unknown whether other specific configurations are exposed","fix":"- Upgrade Traefik 2.x to `2.11.58` or later\n- Upgrade Traefik 3.x to `3.7.13` or later\n- Until patched, remove negated `!Host()` router rules on routes protected by client-certificate verification (unknown whether this fully mitigates)","status":"open","published_at":"2026-10-22T02:16:57+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","triaged_at":"2026-10-25T03:16:18+00:00","updated_at":"2026-10-25T03:16:18+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-25T03:16:18Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Traefik 2.x to `2.11.58` or later\n- Upgrade Traefik 3.x to `3.7.13` or later\n- Until patched, remove negated `!Host()` router rules on routes protected by client-certificate verification (unknown whether this fully mitigates)","reach":"internet","title":"Traefik: negated Host rules let clients skip client-certificate checks","impact":"high","summary":"Traefik before 2.11.58 and 3.7.13 counts negated Host matchers as served domains, which can create a TLS options conflict that falls back to default options. An unauthenticated client can then reach backends that were meant to require verified client certificates.","category":"infrastructure","nicknames":[],"who_cares":["traefik","self-hosted","kubernetes","mtls"],"confidence":0.6,"needs_auth":"no","worst_case":"Unauthenticated clients reach backends protected by client-certificate checks.","analyst_note":"Confirm the exact conflict condition and whether a config-only mitigation exists; check the NVD entry and Traefik release notes for 2.11.58 and 3.7.13.","how_to_check":"- Run `traefik version` (or check the container image tag) and compare against `2.11.58` and `3.7.13`\n- Look for routers using `!Host(` rules alongside `RequireAndVerifyClientCert` TLS options in the dynamic configuration\n- unknown whether other specific configurations are exposed","needs_analyst":true,"not_affected_if":["patched-version","no-client-cert-auth","no-negated-host-rules"],"who_is_affected":"Deployments where Traefik terminates TLS for backends that depend on RequireAndVerifyClientCert for access control, and where a router uses a negated Host matcher that creates a TLS options conflict. Setups that do not rely on client certificates at the proxy, or that run patched versions, can skip this.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000682,"input_tokens":3388,"output_tokens":686,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-114656':14A,17A '-2026':13A,16A '2.11.58':27B,67C '3.7.13':29B,69C 'allow':76C 'attack':94C 'authent':72C 'back':46B,114C 'backend':56B,97C 'bypass':73C 'certif':10A,64B,83C 'check':11A,84C 'client':6A,9A,52B,63B,78C,82C 'client-certif':8A,81C 'conflict':43B,111C 'contain':70C 'count':30B,90C 'creat':39B,107C 'cve':12A,15A 'default':48B,117C 'domain':36B,93C 'fall':45B,113C 'host':3A,23B,32B,87C,106C 'infrastructur':18B 'kubernet':19B 'let':5A 'matcher':33B,88C 'meant':59B 'mtls':20B 'negat':2A,31B,86C 'option':42B,49B,110C,118C 'protect':98C 'reach':55B,96C 'requir':61B 'requireandverifyclientcert':100C 'router':103C 'rule':4A,104C 'self':22B 'self-host':21B 'serv':35B,92C 'skip':7A,80C 'tls':41B,109C 'traefik':1A,24B,25B,65C 'unauthent':51B,77C 'verifi':62B 'vulner':74C","nicknames":[],"mitigations":[],"who_affected":"Deployments where Traefik terminates TLS for backends that depend on RequireAndVerifyClientCert for access control, and where a router uses a negated Host matcher that creates a TLS options conflict. Setups that do not rely on client certificates at the proxy, or that run patched versions, can skip this.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-22T02:16:57+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:L/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":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-114656","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-114656","severity":null,"published_at":"2026-10-22T02:16:57+00:00","modified_at":"2026-10-22T15:39:30+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","fetched_at":"2026-10-23T22:29:02+00:00","note":null},{"source":"epss","external_id":"CVE-2026-114656","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-114656","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T07:15:52+00:00","fetched_at":"2026-10-24T07:15:52+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"}