PT-2025-51619 · Linux+3 · Linux Kernel+3
Published
2025-12-16
·
Updated
2026-05-11
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CVE-2025-68206
None
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Name of the Vulnerable Software and Affected Versions
Linux kernel (affected versions not specified)
Description
The Linux kernel contains an issue within the netfilter module related to Network Address Translation (NAT) and connection tracking (conntrack). Specifically, the problem arises when handling FTP traffic utilizing PASV/EPSV modes, where sequence adjustments are necessary due to payload rewriting (IP and port) on the FTP control connection. This can lead to incorrect TCP length and sequence/acknowledgment sequence calculations. The issue manifests when the FTP helper is assigned after the Dynamic NAT (dnat) setup, resulting in a missing call to
nfct seqadj ext add(). This can cause connection failures, as demonstrated by a "Service not available" error when attempting to list files via FTP in passive mode. The problem is observed in kernel logs with a warning message indicating the missing nfct seqadj ext add() setup call. The issue impacts systems using the ftp helper with NAT rules involving port 21.Recommendations
At the moment, there is no information about a newer version that contains a fix for this vulnerability.
Exploit
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Related Identifiers
Affected Products
Debian
Linuxmint
Linux Kernel
Ubuntu