As per our network monitoring device, One of the Catalyst 6807 in the network have 2 vlans assigned to SVI interface . I am not sure if this is misconfiguration . I wanted to know if this is possible to assign multiple vlans to an SVI .
No, this doesn't make sense. An SVI is the virtual interface entity in a VLAN. If you want interfaces in two different VLANs you need to create two SVIs.
I think you've confused VRFs and SVIs. VRFs can handle the routing for multiple SVIs, segregating the traffic from some VLANs from others.
Every SVI is just an IP address in a Layer 3 VLAN, so, you can have more than one IP on an SVI, but each SVI is in its own VLAN.
Think of it like this: each VLAN can get a virtual interface it is applied to, which can be assigned IP address(es) and Net Mask(s).
It would be like assigning an IP address to a given physical port, but instead it's to a virtual port, you can't put that port into two VLANs without it being a trunk, and a trunk port can't have an IP address assigned to it.
So each Layer 3 VLAN is basically a virtual Access-port assigned to the given access VLAN, assigned a given IP address.
The syntax even lends itself to this interpretation:
int vlan 300 description SVI_VAN_300 ip address 10.10.10.1 255.255.255.0 ip address 10.10.10.254 255.255.255.0 secondary
Very similar to the traditional port:
int e1/48/2 description routed port on vlan 300 switchport mode access switchport access vlan 300 ip address 10.10.10.1 255.255.255.0 ip address 10.10.10.254 255.255.255.0 secondary
You can't set a VLAN interface into access mode or assign it to a VLAN because that's inherent.