Heroku recently learned of and resolved a security vulnerability. We want to report this to you, describe how we responded to the incident, and reiterate our commitment to constantly improving the security and integrity of your data and source code.
On December 19, 2012, security researcher Stephen Sclafani notified us of an issue in our account creation system. Using a maliciously-crafted HTTP request, an attacker could change the password of a pre-existing Heroku user account, and thus gain control of it. This attack would not disclose the pre-existing password to the attacker (those are stored internally as non-recoverable bcrypt hashes).
Upon receiving notification, our engineering and security staff engaged with Mr. Sclafani. We developed and deployed a preliminary patch to production on December 20. While we were deploying the patch, Mr. Sclafani also discovered a related issue in the password reset flow that could be used to reset the passwords of a certain subset of users at random. A preliminary patch for this was also developed and deployed on December 20.
After deploying these patches, we conducted a thorough and comprehensive audit of our internal logs. We found no evidence that these vulnerabilities were exploited prior to Mr. Sclafani’s research on December 19, either by him or any other third parties. Due to the nature of the vulnerability, any customer whose account was compromised would have found both their existing password and API key invalidated, and would have had to initiate a password reset.
While both Mr. Sclafani and Heroku endeavoured to use test accounts exclusively, a very small number of customer account passwords were reset during the incident. We have contacted the impacted customers and advised them to reset their passwords and credentials.
We would like to thank Mr. Sclafani for notifying us of this vulnerability, and giving us ample opportunity to fix it. His description is available at http://stephensclafani.com/2013/01/09/vulnerabilities-in-heroku/. We are extremely grateful to both him and all external security researchers who practice responsible disclosure.
We are confident in the steps we have taken to protect our customers from this vulnerability and will continue to improve our internal processes in order to provide our customers with a trusted cloud platform. We would also like to reaffirm our commitment to the security and integrity of our customers’ data and code. Nothing is more important to us.
Oren Teich, Chief Operating Officer