This means you can never fetch something (even if it's fetchable) because the corrupted data has been cached.
This happens sometimes, but not sure under what conditions.
Note that not caching 404 (or other errors) results makes it possible for the user to trigger the request again, and this could potentially be a problem (there could be too many requests). (Although nothing prevents the user from triggering non-cached requests, so this vulnerability is not just related to caching).
This means you can never fetch something (even if it's fetchable) because the corrupted data has been cached.
This happens sometimes, but not sure under what conditions.
Note that not caching 404 (or other errors) results makes it possible for the user to trigger the request again, and this could potentially be a problem (there could be too many requests). (Although nothing prevents the user from triggering non-cached requests, so this vulnerability is not just related to caching).