The Indian CA eMudhra Limited has eight TLS certificates with laughably weak private keys:
The compromised eMudhra keys were defective at a level that’s challenging the imagination of many of the engineers studying the incident. A normal size for a NIST P-384 elliptic curve cryptography private key contains roughly 384 bits of entropy, a size allowing almost 2384, or a number with 116 digits, different possibilities. The private key sizes of the compromised keys ranged from 3 to 8 bits. Astonishingly, the private keys were 4, 56, 66, 115, 155, 156, 230, 237.
“That is extremely in the ‘this should not be possible’ category,” Valdorda said. “Maybe some horribly dangerous key generation interface has a ‘size’ parameter and they set it to 1 by mistake???”
Ben Cartwright-Cox, director of BGP.tools, said: “My guess is that it’s example code that accidentally leaked to production, but hard to know. But it’s bonkers that no one noticed.”
At this early stage, the most immediate threat appears to be for those using VPNs, especially in countries with governments likely to maliciously intercept traffic. There are likely many other cases for concern. End users largely have no recourse other than to hold off using many non-browser forms of TLS communication until they receive assurances updates are in place.
The whole certificate regime has long been a mess:
The incident is the latest to expose a fatal flaw in the TLS regimen. It’s only as strong as its weakest link, which in this case was eMudhra. Fortunately, transparency logs account for much of that failure, but this measure requires parties to actively monitor massive feeds and works only after unauthorized certificates have been issued. eMudhra representatives weren’t immediately available to answer questions.
One caveat: exploiting compromised certificates requires an active adversary-in-the-middle attack, meaning the attacker must act as a proxy between two TLS parties and receive encrypted traffic, decrypt it, reencrypt it, and send it to the other party. Such capabilities, in some cases, are usually limited to only the most well-resourced attackers. People with control of a local networkat a coffee shop, university, or other organizationface much less of a challenge.
Cleanup of this is going to be another mess—and it’s right on top of the PHP vulnerabilities.
Some more information.