[FD] [RT-SA-2015-003] Alcatel-Lucent OmniSwitch Web Interface Weak Session ID

Advisory: Alcatel-Lucent OmniSwitch Web Interface Weak Session ID During a penetration test, RedTeam Pentesting discovered a vulnerability in the management web interface of an Alcatel-Lucent OmniSwitch 6450. This interface uses easily guessable session IDs, which allows attackers to authenticate as a currently logged-in user and perform administrative tasks. Details ======= Product: Alcatel-Lucent OmniSwitch 6450, 6250, 6850E, 9000E, 6400, 6855 Affected Versions: AOS 6.4.5.R02 AOS 6.4.6.R01 AOS 6.6.4.R01 AOS 6.6.5.R02 Fixed Versions: AOS 6.6.5.80.R02 AOS 6.6.4.309.R01 Vulnerability Type: Session Management - low identifier entropy Security Risk: high Vendor URL: http://ift.tt/1BYu8wm Vendor Status: fixed version released Advisory URL: http://ift.tt/1BYu5Rj Advisory Status: published CVE: CVE-2015-2804 CVE URL: http://ift.tt/1BYu8wn Introduction ============ "The Alcatel-Lucent OmniSwitch 6450 Gigabit and Fast Ethernet Stackable LAN Switches are the latest value stackable switches in the OmniSwitch family of products. The OmniSwitch 6450 was specifically built for versatility offering optional upgrade paths for 10 Gigabit stacking, 10 Gigabit Ethernet uplinks, from Fast to Gigabit user ports (L models) and Metro Ethernet services." (from the vendor's homepage) More Details ============ The management web interface of the OmniSwitch 6450 can be accessed using a web browser via HTTP. A switch with the example IP 192.0.2.1 is accessible via the following URL: http://192.0.2.1/ A client is then redirected to the following URL: http://ift.tt/1Kp9hJF For unauthenticated users the URL displays a login form and sets a session cookie with a session ID. A request to the URL with the command line HTTP client cURL shows the Set-Cookie header: $ curl -I http://ift.tt/1Kp9hJF HTTP/1.1 200 OK Date: Tue, 17 Mar 2015 08:25:42 GMT Server: Agranat-EmWeb/R5_2_4 [...] Set-Cookie: session=sess_11012;PATH=/ The session cookie has the name "session" and its value begins with the string "sess_". By repeatedly requesting the URL with cURL it became obvious that the suffix is always a number between 1 and 32,000. This suggests that there are only about 32,000 possible session IDs, resulting in only 15 bits of entropy. Our tests showed that it was possible to get a throughput of about 50 HTTP requests per second, this means that in order to try every possible session ID an attacker will need at most 11 minutes. On average, the time it takes to find a valid session ID for an active user is even lower. Proof of Concept ================ For an attacker it is very easy to distinguish between a valid and an invalid session ID by looking at the HTTP response size. During our tests, requesting an invalid session ID always returned the login form, which was 3027 bytes in length. With a valid session ID, the management web interface is returned by the webserver and the response is larger. A number of requests in the range of the possible session cookies can be easily executed using wfuzz [0]:

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