default kernels in cnn in keras?
The initial value of the CNN kernels can be seen from the documentation found here.

The default Conv2D layer looks like

keras.layers.Conv2D(32, (5, 5), activation='relu', kernel_initializer='glorot_uniform', bias_initializer='zeros')


So we see that the kernel weights are initialized by Glorot uniform method an dthe bias is initialized as all zeros. 

Glorot Uniform

Uniform sampling from $[-limit, limit]$ where 

$limit = \sqrt{\frac{6}{fan\_in + fan\_out}}$

where $fan\_in$ is the number of input neurons to the weight tensor and $fan\_out$ is the number of output neurons of the weight tensor.