---
id: "CVE-2026-129126"
page: "https://infrastack.ai/live/CVE-2026-129126"
kind: "vulnerability"
aliases: ["CVE-2026-129126"]
title: "C-Kermit: heap overflow in putsrv lets malicious peers write memory"
severity: "critical"
cvss: 9.2
epss: null
exploited: false
status: "open"
category: "runtime"
products: [{"name": "C-Kermit", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["c-kermit", "file-transfer", "kermit", "runtime"]
not_affected_if: ["c-kermit-11.1.515-or-later"]
published_at: "2026-11-13T17:17:29+00:00"
first_seen_at: "2026-11-13T17:48:01+00:00"
updated_at: "2026-11-13T17:48:39+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-129126", "first_seen_at": "2026-11-13T17:48:01+00:00"}]
exploit_sources: []
---

# C-Kermit: heap overflow in putsrv lets malicious peers write memory

Link for people: https://infrastack.ai/live/CVE-2026-129126 (this .md is for agents)

C-Kermit before 11.1.515 has a heap buffer overflow in putsrv() in ckcfns.c. A malicious peer sending crafted Kermit packets with repeat-count compression can write attacker-chosen bytes past the srvcmd heap buffer on servers or receiving instances.

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

## Affected

- vendor:C-Kermit affected range not listed fixed no fixed version listed

## How to check

- Check the installed C-Kermit version with `kermit` and confirm whether it is below `11.1.515`.
- Look for C-Kermit running in server mode or accepting incoming transfers, since the sources say servers and receiving instances are affected.

## Fix

- C-Kermit: `11.1.515`

## Timeline

- 2026-11-13T17:48:01+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-129126

## Documents

- [advisory] Vendor advisory: github.com https://github.com/OpenKermit/ckermit/security/advisories/GHSA-c5px-7h4c-gj8p
- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/c-kermit-before-11.1.515-heap-buffer-overflow-via-putsrv-packet-decoding
- [fix] Patch: github.com https://github.com/OpenKermit/ckermit/commit/37e54720779237897bc6887efac42fe138817897
- [fix] Release notes: github.com https://github.com/OpenKermit/ckermit/releases/tag/v11.1.515

## From the sources

C-Kermit before 11.1.515 contains a heap buffer overflow vulnerability in putsrv() in ckcfns.c that allows malicious peers to write past the srvcmd buffer by sending crafted packets. Attackers can use Kermit repeat-count compression in server command, GET, or file-header packets to write attacker-chosen bytes beyond the heap buffer on servers or receiving instances.

---

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