An issue was discovered in OpenSSH 7.9.
Date: 2019-01
Affected: openbsd/openssh, winscp/winscp, canonical/ubuntu_linux, debian/debian_linux
Attack vector: path-traversal
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2019-6111
CWE: CWE-22
CVSS: 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N)

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/authorized_keys file).


Mitigations:

Architectural layers (MAESTRO):