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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://enterprise.alcatel-lucent.com/?product=OmniSwitch6450&page=overview Vendor Status: fixed version released Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2015-003 Advisory Status: published CVE: CVE-2015-2804 CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-2804 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://192.0.2.1/web/content/index.html 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://192.0.2.1/web/content/index.html 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]: ------------------------------------------------------------------------ ./wfuzz.py -z range,1-32000 --hl 3027 -H "Cookie: session=sess_FUZZ" http://192.0.2.1/web/content/index.html ------------------------------------------------------------------------ Workaround ========== Administrators should avoid using the management web interface and use the serial console or administrate the switch over SSH instead. The web interface can be disabled by executing the following commands: no ip service http no ip service secure-http If the web interface is needed, it must be ensured that only authorised persons are able to even connect to the web server. In addition, the HTTP session timeout can be lowered to one minute with the following command: session timeout http 1 Fix === Upgrade the firmware to a fixed version. Security Risk ============= The vulnerability poses a high risk. An attacker can easily authenticate to a switch with the privileges of another user who is currently logged in. The attack is simple and fast. The only precondition is that a user is already using the switch during the attack. Attackers might actively trick administrators into logging in by social engineering. Timeline ======== 2015-03-16 Vulnerability identified 2015-03-25 Customer approves disclosure to vendor 2015-03-26 CVE number requested 2015-03-31 CVE number assigned 2015-04-01 Vendor notified 2015-04-02 Vendor acknowledged receipt of advisories 2015-04-08 Requested status update from vendor, vendor is investigating 2015-04-29 Requested status update from vendor, vendor is still investigating 2015-05-22 Requested status update from vendor 2015-05-27 Vendor is working on the issue 2015-06-05 Vendor notified customers 2015-06-08 Vendor provided details about affected versions 2015-06-10 Advisory released References ========== [0] https://github.com/xmendez/wfuzz RedTeam Pentesting GmbH Source