In OpenSSH 7.9, due to accepting and displaying arbitrary stderr output from the server, a malicious server (or Man-in-The-Middle attacker) can manipulate the client output, for example to use ANSI control codes to hide additional files being transferred.

An issue was discovered in OpenSSH 7.9. Due to the scp implementation being derived from 1983 rcp, the server chooses which files/directories are sent to the client. However, the scp client only performs cursory validation of the object name returned (only directory traversal attacks are prevented). A malicious scp server (or Man-in-The-Middle attacker) can overwrite arbitrary files in the scp client target directory. If recursive operation (-r) is performed, the server can manipulate subdirectories as well (for example, to overwrite the .ssh/authorizedkeys file).

In OpenSSH 7.9, scp.c in the scp client allows remote SSH servers to bypass intended access restrictions via the filename of . or an empty filename.

Upstream Patch:

https://github.com/openssh/openssh-portable/commit/6010c030 https://cvsweb.openbsd.org/cgi-bin/cvsweb/src/usr.bin/ssh/scp.c.diff?r1=1.197&r2=1.198&f=h

Last updated 25 August 2025

An issue was discovered in OpenSSH 7.9. Due to missing character encoding in the progress display, a malicious server (or Man-in-The-Middle attacker) can employ crafted object names to manipulate the client output, e.g., by using ANSI control codes to hide additional files being transferred. This affects refreshprogressmeter() in progressmeter.c.

OpenSSH-portable (OpenSSH) 3.6.1p1 and earlier with PAM support enabled immediately sends an error message when a user does not exist, which allows remote attackers to determine valid usernames via a timing attack.