CVE-2026-129122

Description

C-Kermit 6.0.192 before 11.1.515 contains a buffer overflow vulnerability in tn_snenv() in ckctel.c that allows malicious Telnet servers to corrupt client memory via crafted NEW-ENVIRON SEND subnegotiation. Malicious or machine-in-the-middle servers can send oversized variable names before authentication, overflowing a 16-byte stack buffer and a miscomputed heap buffer to corrupt stack and heap memory.

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

• 7.7CVSS 4.0, Highfrom the CNA (VulnCheck)CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
• 7.5CVSS 3.1, Highfrom the CNA (VulnCheck)CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

No explicit remediation statement is available on this page yet. Consult the original record and vendor references before choosing a fix.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Timeline

1. 13 Nov 2026 Published

Weakness

• CWE-787

References

• GitHub Security Advisory (GHSA-c5px-7h4c-gj8p)vendor-advisory
• github.compatch
• github.compatch
• C-Kermit v11.1.515 Release Notesrelease-notes
• github.comtechnical-description
• VulnCheck Advisory: C-Kermit 6.0.192 before 11.1.515 Buffer Overflow via Telnet NEW-ENVIRON Negotiationthird-party-advisory