---
id: "CVE-2026-129117"
page: "https://infrastack.ai/live/CVE-2026-129117"
kind: "vulnerability"
aliases: ["CVE-2026-129117"]
title: "C-Kermit: Telnet TLS check skips server name, letting attackers impersonate servers"
severity: "high"
cvss: 7.6
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["c-kermit", "other", "telnet", "tls"]
not_affected_if: ["no-c-kermit", "not-telnet"]
published_at: "2026-11-13T17:17:28+00:00"
first_seen_at: "2026-11-13T17:48:00+00:00"
updated_at: "2026-11-13T17:48:52+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-129117", "first_seen_at": "2026-11-13T17:48:00+00:00"}]
exploit_sources: []
---

# C-Kermit: Telnet TLS check skips server name, letting attackers impersonate servers

Link for people: https://infrastack.ai/live/CVE-2026-129117 (this .md is for agents)

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.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `kermit` and check the version banner; versions 8.0.200 up to but not including `11.1.515` are affected.
- 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).

## Timeline

- 2026-11-13T17:48:00+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-129117

## Documents

- [advisory] Vendor advisory: github.com https://github.com/OpenKermit/ckermit/security/advisories/GHSA-5pc4-gh6q-5h4w
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/c-kermit-8.0.200-before-11.1.515-missing-hostname-verification-in-authentication-ssl
- [fix] Patch: github.com https://github.com/OpenKermit/ckermit/commit/0008b429e4fadc8ecfd3d7d661fd55d72e26d527
- [fix] Release notes: github.com https://github.com/OpenKermit/ckermit/releases/tag/v11.1.515

## From the sources

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.

---

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