Substituting such values in extension scripts facilitated SQL injection
when @extowner@, @extschema@, or @extschema:...@ appeared inside a
quoting construct (dollar quoting, '', or ""). No bundled extension was
vulnerable. Vulnerable uses do appear in a documentation example and in
non-bundled extensions. Hence, the attack prerequisite was an
administrator having installed files of a vulnerable, trusted,
non-bundled extension. Subject to that prerequisite, this enabled an
attacker having database-level CREATE privilege to execute arbitrary
code as the bootstrap superuser. By blocking this attack in the core
server, there's no need to modify individual extensions. Back-patch to
v11 (all supported versions).
Reported by Micah Gate, Valerie Woolard, Tim Carey-Smith, and Christoph
Berg.
Security: CVE-2023-39417
f53511010b