pgAdmin 4 uses a file-based session management approach. The session files are saved on disk as pickle objects. When a user performs a request, the value of the session cookie 'pga4_session' is used to retrieve the file, then its content is deserialised, and finally its signature verified. The cookie value is split in 2 parts at the first '!' character. The first part is the session ID (sid), while the second is the session digest. The vulnerability lies in versions of pgAdmin prior to 8.4 where a method loads session files by concatenating the sessions folder - located inside the pgAdmin 4 DATA_DIR - with the session ID. Precisely, the two values are concatenated using the ['os.path.join'] function. It does not set a trusted base-path which should not be escaped https://github.com/pgadmin-org/pgadmin4/issues/7258
Created pgadmin4 tracking bugs for this issue: Affects: fedora-all [bug 2268536]