Vulnerability record
CVE-2026-129122
The short answer
CVE-2026-129122 affects OpenKermit C-Kermit and is rated high (CVSS 7.7). It is not in CISA's Known Exploited Vulnerabilities catalog.
What it is
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.
Weakness: CWE-787.
Severity
7.7 high
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/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
Exploited (CISA KEV)
Not listed
CISA lists confirmed exploitation only
EPSS, next 30 days
No score
FIRST scores CVEs within a day of publication
How it can be exploited
- Attack vector
- Network
- Attack complexity
- High
- Attack requirements
- None
- Privileges required
- None
- User interaction
- Passive
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Affected products
C-Kermit. NVD's record lists the exact affected versions.
References
- github.com/OpenKermit/ckermit/blob/v11.0.514/ckctel.c#L5622
- github.com/OpenKermit/ckermit/commit/39ab009a365b97632e9975e1266fa618c4bdc59f
- github.com/OpenKermit/ckermit/commit/42cf6decb926f56d606a76262791aaf071955d25
- github.com/OpenKermit/ckermit/releases/tag/v11.1.515
- github.com/OpenKermit/ckermit/security/advisories/GHSA-c5px-7h4c-gj8p
- www.vulncheck.com/advisories/c-kermit-6.0.192-before-11.1.515-buffer-overflow-via-telnet-new-environ-negotiation
Questions
Is CVE-2026-129122 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog as of 2026-11-13.
How do I fix CVE-2026-129122?
Follow the vendor advisory in the references below. NVD lists the affected versions under its configurations.
From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Received. The description is NVD's text, quoted as published.
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