The do_extendedOp function in ibmslapd in IBM Tivoli Directory Server (TDS) 6.0 before 6.0.0.62 (aka 6.0.0.8-TIV-ITDS-IF0004) on Linux, Solaris, and Windows allows remote authenticated users to cause a denial of service (ABEND) via a malformed LDAP extended operation that triggers certain comparisons involving the NULL operation OID.