{"id":"CVE-2026-129117","kind":"vulnerability","aliases":["CVE-2026-129117"],"related":[],"title":"C-Kermit: Telnet TLS check skips server name, letting attackers impersonate servers","description":"C-Kermit 8.0.200 before 11.1.515 contains an improper certificate validation vulnerability that allows machine-in-the-middle attackers to impersonate Telnet servers because ssl_reply() never calls ssl_check_server_name(). Attackers can refuse START-TLS, offer Telnet AUTHENTICATION SSL, and present any trusted CA certificate to capture user credentials and session data.","summary":"C-Kermit before 11.1.515 does not check the server name on the certificate during a Telnet TLS handshake. A machine-in-the-middle attacker can present any trusted CA certificate, impersonate the Telnet server, and capture user credentials and session data.","severity":"high","cvss":7.6,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["c-kermit","other","telnet","tls"],"not_affected_if":["no-c-kermit","not-telnet"],"how_to_check":"- Run `kermit` and check the version banner; versions 8.0.200 up to but not including `11.1.515` are affected.\n- Look for Telnet connections that use START-TLS or AUTHENTICATION SSL in scripts or configs.","fix":"- C-Kermit: move to `11.1.515` or later (per the NVD range before 11.1.515).","status":"open","published_at":"2026-11-13T17:17:28+00:00","first_seen_at":"2026-11-13T17:48:00+00:00","triaged_at":"2026-11-13T17:48:52+00:00","updated_at":"2026-11-13T17:48:52+00:00","category":"other","confidence":0.6,"triage":{"at":"2026-11-13T17:48:52Z","model":"claude-haiku-5-5","output":{"fix":"- C-Kermit: move to `11.1.515` or later (per the NVD range before 11.1.515).","reach":"network","title":"C-Kermit: Telnet TLS check skips server name, letting attackers impersonate servers","impact":"high","summary":"C-Kermit before 11.1.515 does not check the server name on the certificate during a Telnet TLS handshake. A machine-in-the-middle attacker can present any trusted CA certificate, impersonate the Telnet server, and capture user credentials and session data.","audience":"businesses","category":"other","nicknames":[],"who_cares":["c-kermit","telnet","tls"],"confidence":0.6,"fix_status":"available","needs_auth":"no","worst_case":"Attacker captures credentials and session data through impersonated Telnet server","analyst_note":"Confirm the exact affected Telnet/TLS code path and whether default builds use START-TLS; check the vendor advisory and release notes linked from NVD.","how_to_check":"- Run `kermit` and check the version banner; versions 8.0.200 up to but not including `11.1.515` are affected.\n- Look for Telnet connections that use START-TLS or AUTHENTICATION SSL in scripts or configs.","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":["not-telnet","no-c-kermit"],"who_is_affected":"Teams that use C-Kermit as a Telnet client over TLS, especially from untrusted networks where a machine-in-the-middle attacker could sit between client and server. Systems that do not use C-Kermit for Telnet, or that run only on trusted networks, are less exposed. The sources do not say how common Telnet TLS use is among C-Kermit users.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000779,"input_tokens":4660,"output_tokens":626,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-129117':16A,19A '-2026':15A,18A '11.1.515':30B,74C '8.0.200':72C 'allow':82C 'attack':11A,51B,88C,102C 'authent':110C 'c':2A,21B,27B,70C 'c-kermit':1A,20B,26B,69C 'ca':56B,116C 'call':97C 'captur':63B,119C 'certif':39B,57B,78C,117C 'check':6A,33B,99C 'contain':75C 'credenti':65B,121C 'cve':14A,17A 'data':68B,124C 'handshak':44B 'imperson':12A,58B,90C 'improp':77C 'kermit':3A,22B,28B,71C 'let':10A 'machin':47B,84C 'machine-in-the-middl':46B,83C 'middl':50B,87C 'name':9A,36B,101C 'never':96C 'offer':108C 'present':53B,113C 'refus':104C 'repli':95C 'server':8A,13A,35B,61B,92C,100C 'session':67B,123C 'skip':7A 'ssl':94C,98C,111C 'start':106C 'start-tl':105C 'telnet':4A,24B,42B,60B,91C,109C 'tls':5A,25B,43B,107C 'trust':55B,115C 'user':64B,120C 'valid':79C 'vulner':80C","nicknames":[],"mitigations":[],"who_affected":"Teams that use C-Kermit as a Telnet client over TLS, especially from untrusted networks where a machine-in-the-middle attacker could sit between client and server. Systems that do not use C-Kermit for Telnet, or that run only on trusted networks, are less exposed. The sources do not say how common Telnet TLS use is among C-Kermit users.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["ckermit","high","other","telnet","tls"],"campaign_type":null,"search_a":"'-129117':16A,19A '-2026':15A,18A 'attack':11A 'c':2A 'c-kermit':1A 'check':6A 'cve':14A,17A 'imperson':12A 'kermit':3A 'let':10A 'name':9A 'server':8A,13A 'skip':7A 'telnet':4A 'tls':5A","search_b":"'11.1.515':30B 'attack':51B 'c':21B,27B 'c-kermit':20B,26B 'ca':56B 'captur':63B 'certif':39B,57B 'check':33B 'credenti':65B 'data':68B 'handshak':44B 'imperson':58B 'kermit':22B,28B 'machin':47B 'machine-in-the-middl':46B 'middl':50B 'name':36B 'present':53B 'server':35B,61B 'session':67B 'telnet':24B,42B,60B 'tls':25B,43B 'trust':55B 'user':64B","search_c":"'11.1.515':74C '8.0.200':72C 'allow':82C 'attack':88C,102C 'authent':110C 'c':70C 'c-kermit':69C 'ca':116C 'call':97C 'captur':119C 'certif':78C,117C 'check':99C 'contain':75C 'credenti':121C 'data':124C 'imperson':90C 'improp':77C 'kermit':71C 'machin':84C 'machine-in-the-middl':83C 'middl':87C 'name':101C 'never':96C 'offer':108C 'present':113C 'refus':104C 'repli':95C 'server':92C,100C 'session':123C 'ssl':94C,98C,111C 'start':106C 'start-tl':105C 'telnet':91C,109C 'tls':107C 'trust':115C 'user':120C 'valid':79C 'vulner':80C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-10-31T01:36:55+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/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-2026-129117","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-129117","severity":null,"published_at":"2026-11-13T17:17:28+00:00","modified_at":"2026-11-13T17:17:28+00:00","first_seen_at":"2026-11-13T17:48:00+00:00","fetched_at":"2026-11-13T17:48:00+00:00","note":null}],"documents":[{"id":148079,"url":"https://github.com/OpenKermit/ckermit/commit/0008b429e4fadc8ecfd3d7d661fd55d72e26d527","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":148076,"url":"https://github.com/OpenKermit/ckermit/releases/tag/v11.1.515","title":"Release notes: github.com","kind":"release","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Release notes: github.com"},{"id":148077,"url":"https://github.com/OpenKermit/ckermit/security/advisories/GHSA-5pc4-gh6q-5h4w","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-10-31T01:36:55+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":148082,"url":"https://www.vulncheck.com/advisories/c-kermit-8.0.200-before-11.1.515-missing-hostname-verification-in-authentication-ssl","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}