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

High 7.7 Published 31 Jul 2026 Updated 1 Aug 2026

Authenticated users can execute arbitrary OS commands via shell metacharacters in usernames when the MASTER_PASSWORD_HOOK feature is enabled.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-17347?

CVE-2026-17347 is a high-severity command injection vulnerability in pgadmin.org pgAdmin 4, published on 31 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

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.

Weakness: CWE-88, CWE-78

Which versions are affected by CVE-2026-17347?

It affects 1 product.

Products include Pgadmin Pgadmin 4.

How do I fix CVE-2026-17347?

Upgrade to a fixed version.

Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.

Is CVE-2026-17347 being exploited?

There is no known exploitation of CVE-2026-17347 in the wild and no public exploit code.

Sources

Also known as GHSA-f649-fjv9-qgcg.