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

Vulnerability summary

CVE-2026-17347 is a high (CVSS 8.8) vulnerability in pgadmin pgadmin_4. EPSS estimates a 0.72% chance of exploitation in the next 30 days, higher than 53.8% of scored vulnerabilities.

Timeline

1. 31-07-2026
   PublishedVulnerability first disclosed.
2. 01-08-2026
   Last modifiedVulnerability information updated.

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.

• CWE-78Improper Neutralization of Special Elements used in an OS CommandThe product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.
• CWE-88Improper Neutralization of Argument Delimiters in a CommandThe product constructs a string for a command to be executed by a separate component in another control sphere, but it does not properly delimit the intended arguments, options, or switches within that command string.