On April 7, 2014 information was released about a new vulnerability (CVE-2014-0160) in OpenSSL, the cryptography library that powers the vast majority of private communication across the Internet. This library is key for maintaining privacy between servers and clients, and confirming that Internet servers are who they say they are.

This vulnerability, known as Heartbleed, would allow an attacker to steal the keys that protect communication, user passwords, even the system memory of a vulnerable server. This represents a major risk to large portions of private traffic on the Internet, including github.com.

Note: GitHub Enterprise servers are not affected by this vulnerability. They run an older OpenSSL version which is not vulnerable to the attack.

As of right now, we have no indication that the attack has been used against github.com. That said, the nature of the attack makes it hard to detect so we’re proceeding with a high level of caution.

What is GitHub doing about this?

UPDATE: 2014-04-08 16:00 PST – All browser sessions that were active prior to the vulnerability being addressed have been reset. See below for more info.

We’ve completed a number of measures already and continue to work the issue.

  1. We’ve patched all our systems using the newer, protected versions of OpenSSL. We started upgrading yesterday after the vulnerability became public and completed the roll out today. We are also working with our providers to make sure they’re upgrading their systems to minimize GitHub’s exposure.
  2. We’ve recreated and redeployed new SSL keys and reset internal credentials. We have also revoked our older certs just to be safe.
  3. We’ve forcibly reset all browser sessions that were active prior to the vulnerability being addressed on our servers. You may have been logged out and have to log back into GitHub. This was a proactive measure to defend against potential session hijacking attacks that may have taken place while the vulnerability was open.

Prior to this incident, GitHub made a number of enhancement to mitigate attacks like this. We deployed Perfect Forward Secrecy at the end of last year, which makes it impossible to use stolen encryption keys to read old encrypted communication. We are working to find more opportunities like this.

What should you do about Heartbleed right now?

Right now, GitHub has no indication that the vulnerability has been used outside of testing scenarios. However, out of an abundance of caution, you can:

  1. Change your GitHub password. Be sure your password is strong; for more information, see What is a strong password?
  2. Enable Two-Factor Authentication.
  3. Revoke and recreate personal access and application tokens.

Stay tuned

GitHub works hard to keep your code safe. We are continuing to respond to this vulnerability and will post updates as things progress. For more information as it’s available, keep an eye on Twitter or the GitHub Blog.