Public on 2023-03-22
Modified on 2024-01-30
The curl advisory describes this issue as follows:

curl supports SFTP transfers. curl's SFTP implementation offers a special feature in the path component of URLs: a tilde (~) character as the first path element in the path to denotes a path relative to the user's home directory. This is supported because of wording in the once proposed to-become RFC draft that was to dictate how SFTP URLs work.

Due to a bug, the handling of the tilde in SFTP path did however not only replace it when it is used stand-alone as the first path element but also wrongly when used as a mere prefix in the first element.

Using a path like /~2/foo when accessing a server using the user dan (with home directory /home/dan) would then quite surprisingly access the file /home/dan2/foo.

This can be taken advantage of to circumvent filtering or worse.
Medium severity
CVSS v3 Base Score
See breakdown

Affected Packages

Platform Package Release Date Advisory Status
Amazon Linux 1 curl 2023-04-13 ALAS-2023-1729 Fixed
Amazon Linux 2 - Core curl 2023-06-05 ALAS2-2023-2070 Fixed
Amazon Linux 2023 curl 2023-06-05 ALAS2023-2023-193 Fixed

CVSS Scores

Score Type Score Vector
Amazon Linux CVSSv3 4.5 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:L