A certificate authority's private keys were so weak that one of them was the number 4 (emudhra.we-have-a-problem.com)
Eight eMudhra intermediate CA certificates, valid since April 2025, had keys that could be computed from the certificates themselves. A commenter pulled out the scalars: 4, 56, 66, 115, 155, 156, 230, 237.
Firefox shipped a fix in hours via OneCRL; a Mozilla engineer in the thread says everything outside the big browsers is still exposed.