A modified, unauthenticated server can send an unterminated string during the establishment of Kerberos transport encryption. When a libpq client application has a Kerberos credential cache and doesn't explicitly disable option "gssencmode", a server can cause libpq to over-read and report an error message containing uninitialized bytes from and following its receive buffer. If libpq's caller somehow makes that message accessible to the attacker, this achieves a disclosure of the over-read bytes. We have not confirmed or ruled out viability of attacks that arrange for a crash or for presence of notable, confidential information in disclosed bytes.