Jacob Champion discovered that libpq can leak memory contents after GSSAPI transport encryption initiation fails.
A modified server, or an unauthenticated man-in-the-middle, can send a not-zero-terminated error message during setup of GSSAPI (Kerberos) transport encryption. libpq will then copy that string, as well as following bytes in application memory up to the next zero byte, to its error report. Depending on what the calling application does with the error report, this could result in disclosure of application memory contents. There is also a small probability of a crash due to reading beyond the end of memory. Fix by properly zero-terminating the server message. (CVE-2022-41862)
For Debian 10 buster, this problem has been fixed in version 11.19-0+deb10u1.
We recommend that you upgrade your postgresql-11 packages.
For the detailed security status of postgresql-11 please refer to its security tracker page at: https://security-tracker.debian.org/tracker/postgresql-11
Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: https://wiki.debian.org/LTS