Important: postgresql15 security update (Amazon Linux 2023)

Package updates are available for Amazon Linux 2023 that fix the following vulnerabilities: CVE-2023-5870: The documentation says the pg_cancel_backend role cannot signal "a backend owned by a superuser". On the contrary, it can signal background workers, including the logical replication launcher. It can signal autovacuum workers and the autovacuum launcher. Signaling autovacuum workers and those two launchers provides no meaningful exploit, so exploiting this vulnerability requires a non-core extension with a less-resilient background worker. For example, a non-core background worker that does not auto-restart would experience a denial of service with respect to that particular background worker. CVE-2023-5869: While modifying certain SQL array values, missing overflow checks let authenticated database users write arbitrary bytes to a memory area that facilitates arbitrary code execution. Missing overflow checks also let authenticated database users read a wide area of server memory. The CVE-2021-32027 fix covered some attacks of this description, but it missed others. CVE-2023-5868: Certain aggregate function calls receiving "unknown"-type arguments could disclose bytes of server memory from the end of the "unknown"-type value to the next zero byte. One typically gets an "unknown"-type value via a string literal having no type designation. We have not confirmed or ruled out viability of attacks that arrange for presence of notable, confidential information in disclosed bytes.