[oss-security][CVE-2026-8328] CPython: FTP PASV SSRF, ftpcp() does not use actual peer address, trusts server-supplied PASV host address

[Alan Coopersmith <alan.coopersmith () oracle com>]

-------- Forwarded Message --------
Subject: 	[Security-announce][CVE-2026-8328] FTP PASV SSRF, ftpcp() does not use 
actual peer address, trusts server-supplied PASV host address
Date:   Wed, 13 May 2026 20:15:52 +0000
From:   Seth Larson <seth () python org>
Reply-To:       security-sig () python org
To:     security-announce () python org



There is a MEDIUM severity vulnerability affecting CPython.

The ftpcp() function in Lib/ftplib.py was not updated when CVE-2021-4189 was 
fixed. While makepasv() was patched to replace server-supplied PASV host 
addresses with the actual peer address (getpeername()[0]), ftpcp() still calls 
parse227() directly and passes the raw attacker-controllable IP address and port 
to target.sendport().

Please see the linked CVE ID for the latest information on affected versions:

* https://www.cve.org/CVERecord?id=CVE-2026-8328
* https://github.com/python/cpython/pull/149648

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