It is fine, "Caution murmured ..." is being used as a figure of speech. I believe it's called a personification. A personification is "a figure of speech in which an inanimate object or abstraction is endowed with human qualities or abilities." "Caution" here is being treated like a human being, and it whispered to him that he was about to fall into a trap.
Example: That kitchen knife will take a bite out of your hand if you don't handle it safely.
The second last sentence uses one too: "But instinct ... told him ..."
Here is a list of examples of personification.
I however don't understand the absence of a conjunction in the latter part. To me, it seems it needs an "or" before the last element "a trap".
Edit: Response to my query about the sentence not using a conjunction.
James K and Jason Bassford explain in the comments that the absence/omission of "or" is most likely intentional. I am quoting them here just in case the comments are removed.
"The list is truncated because Harry stops worrying about the possibilties and stops thinking mid-way through the list and acts on instinct." - James K
"Omitting the comma there is a stylistic technique called asyndeton." - Jason Bassford
Also, CJ Dennis points out that including the "or" would change the feeling of the sentence: "Using "or" would reduce the impact of the sentence."