Buffer Overflow Vulnerability in C-Kermit by OpenKermit

CVE-2026-129122

What is CVE-2026-129122?

C-Kermit versions prior to 11.1.515 suffer from a buffer overflow vulnerability within the tn_snenv() function in ckctel.c. This weakness enables malicious Telnet servers to exploit crafted NEW-ENVIRON SEND subnegotiation, allowing them to corrupt client memory. Attackers can exploit the vulnerability by sending oversized variable names before authentication occurs, which can overflow a 16-byte stack buffer and mismanaged heap buffer, leading to potential corruption of both stack and heap memory. It is crucial for users of C-Kermit to upgrade to version 11.1.515 or later to mitigate this risk.

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