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Vulnerability record

CVE-2026-129126

criticalCVSS 4.0 9.2Published · OpenKermit

The short answer

CVE-2026-129126 affects OpenKermit C-Kermit and is rated critical (CVSS 9.2). It is not in CISA's Known Exploited Vulnerabilities catalog.

What it is

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.

Weakness: CWE-122.

Severity

9.2 critical

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/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
Low
Attack requirements
Present
Privileges required
None
User interaction
None
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Affected products

C-Kermit. NVD's record lists the exact affected versions.

References

Questions

Is CVE-2026-129126 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog as of 2026-11-14.

How do I fix CVE-2026-129126?

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: Deferred. The description is NVD's text, quoted as published.

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