Valve has confirmed that your Steam password, or other private information, did not leak. On top of that, Valve stated that the leak came from a different source than Steam, and does not provide info linked to your Steam account in any way you need to worry about.
In a statement sent to GameSpot, a Valve representative said “Yesterday we were made aware of reports of leaks of older text messages that had previously been sent to Steam customers. We have examined the leak sample and have determined this was NOT a breach of Steam systems.”
The security company Underdark was the first to report the alleged leaks, writing on LinkedIn that information from 89 million Steam accounts was being sold on the dark web. However, Valve has corrected that, as the leak came from the SMS service that sends temporary two-factor login codes. Valve said that the phone numbers were leaked, but that any information related to your Steam account, including which account the phone numbers are tied to, was not leaked.