What is the maximum length of a X.509 OID?
OIDs don't have a maximal length / depth specified. There is no real value where you can safely cut them off - or rather reject them (raise an exception or error). Anything over 20 bytes seems ridiculous, so that should be plenty. Limiting to a measly 1 KB of RAM should be fine on a non-embedded platform (desktop / server) as well, if you must set a limit.

When planning to protect against DoS attacks from certificates it is more useful to limit the amount of bytes of the entire certificate. It's not very efficient to limit each and every component within the certificate.



When programming in C/unmanaged C++ it is more reasonable to bother about ASN.1 based buffer overruns; those are common enough and extremely dangerous.