Possible Information Leak / Session Hijack Vulnerability in Rack

There's a possible information leak / session hijack vulnerability in Rack. Attackers may be able to find and hijack sessions by using timing attacks targeting the session id. Session ids are usually stored and indexed in a database that uses some kind of scheme for speeding up lookups of that session id. By carefully measuring the amount of time it takes to look up a session, an attacker may be able to find a valid session id and hijack the session. The session id itself may be generated randomly, but the way the session is indexed by the backing store does not use a secure comparison. ### Impact The session id stored in a cookie is the same id that is used when querying the backing session storage engine. Most storage mechanisms (for example a database) use some sort of indexing in order to speed up the lookup of that id. By carefully timing requests and session lookup failures, an attacker may be able to perform a timing attack to determine an existing session id and hijack that session. ## Releases The 1.6.12 and 2.0.8 releases are available at the normal locations. ### Workarounds There are no known workarounds. ### Patches To aid users who aren't able to upgrade immediately we have provided patches for the two supported release series. They are in git-am format and consist of a single changeset. * 1-6-session-timing-attack.patch - Patch for 1.6 series * 2-0-session-timing-attack.patch - Patch for 2.6 series ### Credits Thanks Will Leinweber for reporting this!

Quoted source text, attributed separately from HOL analysis.