AES-256 is indeed cracked, because it doesn't hold its original 256bit security. You ask if it is secure - security isn't a yes/no question, it is 231bit secure, and common wisdom is that 128bit+ is "pretty secure", and 90bit- is close to practically broken.

Jun 24, 2017 What is AES 256 Bit Encryption? Can it be cracked? How safe is a AES 256 Bit Encryption? | VComply Sep 09, 2017

Mar 26, 2010

Jun 11, 2012 NSA has stopped recommending P-256, SHA-256, and AES-128.

Microsoft Office 2013's enhanced protection scheme cracked ahead of official launch Russian corporate security and IT audit firm ElcomSoft claims to have developed tools with the ability to

Is AES-128 and AES-256 broken? - IT Peer Network Mar 26, 2010 cryptography - Why most people use 256 bit encryption Assuming you're talking about AES 128 versus AES 256, there is a known weakness in the key expansion function that affects AES256. Fundamentally, the weakness reduces the complexity of AES256 to that lower than AES128. There's a similar attack for AES192 as well, though in this case, the complexity of AES192 remains greater than AES128.