There is a use-after-free issue in all samba 4.9.x versions before 4.9.18, all samba 4.10.x versions before 4.10.12 and all samba 4.11.x versions before 4.11.5, essentially due to a call to realloc() while other local variables still point at the original buffer.

A vulnerability was found in Samba from version (including) 4.9 to versions before 4.9.6 and 4.10.2. During the creation of a new Samba AD DC, files are created in a private subdirectory of the install location. This directory is typically mode 0700, that is owner (root) only access. However in some upgraded installations it will have other permissions, such as 0755, because this was the default before Samba 4.8. Within this directory, files are created with mode 0666, which is world-writable, including a sample krb5.conf, and the list of DNS names and servicePrincipalName values to update.

A statement in the System Programming Guide of the Intel 64 and IA-32 Architectures Software Developer's Manual (SDM) was mishandled in the development of some or all operating-system kernels, resulting in unexpected behavior for #DB exceptions that are deferred by MOV SS or POP SS, as demonstrated by (for example) privilege escalation in Windows, macOS, some Xen configurations, or FreeBSD, or a Linux kernel crash. The MOV to SS and POP SS instructions inhibit interrupts (including NMIs), data breakpoints, and single step trap exceptions until the instruction boundary following the next instruction (SDM Vol. 3A; section 6.8.3). (The inhibited data breakpoints are those on memory accessed by the MOV to SS or POP to SS instruction itself.) Note that debug exceptions are not inhibited by the interrupt enable (EFLAGS.IF) system flag (SDM Vol. 3A; section 2.3). If the instruction following the MOV to SS or POP to SS instruction is an instruction like SYSCALL, SYSENTER, INT 3, etc. that tra…