The push_ascii function in smbd in Samba 3.6.x before 3.6.24, 4.0.x before 4.0.19, and 4.1.x before 4.1.9 allows remote authenticated users to cause a denial of service (memory corruption and daemon crash) via an attempt to read a Unicode pathname without specifying use of Unicode, leading to a character-set conversion failure that triggers an invalid pointer dereference.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.