A bug in Microsoft’s code due to the change of the calendar year hit the company’s Exchange servers over the weekend, causing them to stop processing emails and leading to frantic efforts to patch the program.
The so-called “Y2K22” bug — the name harkens back to the infamous Y2K scare that rattled tech consumers at the turn of the millennium — temporarily prevented the Exchange software from transferring emails, leading to a backlog of mail that impacted consumers relying on the Microsoft product.
The issue stemmed from Microsoft’s malware-scanning engine. When assigning a number to an update, Microsoft would use the last two digits of the year, the month, and the day, followed by an additional four digits. On January 1, 2022, for instance, the update number could look like this: 2201010001.
The problem with this was that due the technical limitations, this field could only house 31 bits, units of information that can only contain a 0 or 1. Therefore, the maximum number that could be expressed through this system was 2147483648 — 2 to the power of 31 — a number lower than what was output on January 1. Since the update number in the new year exceeded the maximum possible value in this system, the program malfunctioned.
“The problem relates to a date check failure with the change of the new year and is not a failure of the AV engine itself,” Microsoft said in a blog post. “The version checking performed against the signature file is causing the malware engine to crash, resulting in messages being stuck in transport queues.”
A fix to the bug now appears to be operational, but requires some action by the user, either through manually deleting files and updating the program or by downloading an automated script to make the fix.