CVE-2021-3671

Se ha encontrado una desreferencia de puntero null en la forma en que el servidor kerberos de Samba manejaba el sname faltante en TGS-REQ (Ticket Granting Server - Request). Un usuario autenticado podría usar este fallo para bloquear el servidor samba

Isaac Boukris and Andrew Bartlett discovered that Heimdal's KDC was not properly performing checksum algorithm verifications in the S4U2Self extension module. An attacker could possibly use this issue to perform a machine-in-the-middle attack and request S4U2Self tickets for any user known by the application. This issue only affected Ubuntu 14.04 ESM, Ubuntu 16.04 ESM and Ubuntu 18.04 LTS. It was discovered that Heimdal was not properly handling the verification of key exchanges when an anonymous PKINIT was being used. An attacker could possibly use this issue to perform a machine-in-the-middle attack and expose sensitive information. This issue only affected Ubuntu 14.04 ESM, Ubuntu 16.04 ESM and Ubuntu 18.04 LTS.