CVE-2026-17347pgAdmin 4: OS command injection in MASTER_PASSWORD_HOOK via untrusted username substitution

Official description

The MASTER_PASSWORD_HOOK setting, introduced in pgAdmin 4 7.2, lets an administrator configure an external command that returns a per-user encryption key, with %u in the configured string replaced by the current user's name. The previous implementation substituted the username directly into the command string and executed the result with subprocess.Popen(..., shell=True). Because the username can originate from an external authentication source (OAuth/OIDC claims, Kerberos, webserver auth) rather than a value pgAdmin fully controls, a username containing shell metacharacters (';', '$()', backticks, pipes, '&&', newlines) allowed an authenticated user to execute arbitrary commands as the pgAdmin service account in any deployment where the configured hook string uses %u. Fix tokenises the trusted, administrator-configured hook string into an argument vector first (using shlex in POSIX-quoting mode, with backslash-escaping disabled so Windows-style paths are not mis-parsed), substitutes the untrusted username into the individual argv elements, and executes with shell=False. The username is therefore always confined to a single argv element; any shell metacharacters it contains are inert. Administrators whose MASTER_PASSWORD_HOOK previously relied on shell features (pipes, redirection, environment-variable expansion, globbing) within the hook string itself must move that logic into the invoked script, since it is no longer interpreted by a shell. This issue affects pgAdmin 4: from 7.2 before 9.17.

Affected products (as reported)

References

• https://github.com/pgadmin-org/pgadmin4/issues/10191 issue-tracking
• https://github.com/pgadmin-org/pgadmin4/commit/ea7e798aac27174d2bacee1d6e136bed76a95e23 patch
• https://github.com/pgadmin-org/pgadmin4/commit/e7a85767314e7b0fe0b35fe80b9c1af38f48dff6 patch