Cisco Ironport WSA telnetd Remote Code Execution

Cisco Ironport WSA Telnetd Remote Code Execution Vulnerability
Vendor: Cisco
Product web page: http://www.cisco.com
Affected version: Cisco Ironport WSA - AsyncOS 8.0.5 for Web build 075
Date: 22/05/2014
Credits: Glafkos Charalambous
CVE: CVE-2011-4862
CVSS Score: 7.6
Impact: Unauthenticated Remote Code Execution with elevated privileges
Description: The Cisco Ironport WSA virtual appliances are vulnerable to an old FreeBSD telnetd encryption Key ID buffer overflow which allows remote attackers to execute arbitrary code (CVE-2011-4862).
Cisco WSA Virtual appliances have the vulnerable telnetd daemon enabled by default. 

diff --git a/ChangeLog b/ChangeLog
index dd381d1..f4e4457 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2011-12-25  Alfred M. Szmidt  <[email protected]>
+
+* libtelnet/encrypt.c (encrypt_keyid): Make sure that LEN never is
+greater than MAXKEYLEN.
+
 2011-12-22  Mats Erik Andersson <[email protected]>
 
 * libinetutils/setsig.c (setsig) [HAVE_SIGACTION]: Initialize
diff --git a/libtelnet/encrypt.c b/libtelnet/encrypt.c
index 06827d9..abfa6d4 100644
--- a/libtelnet/encrypt.c
+++ b/libtelnet/encrypt.c
@@ -796,6 +796,9 @@ encrypt_keyid (kp, keyid, len)
   int dir = kp->dir;
   register int ret = 0;
 
+  if (len > MAXKEYLEN)
+    len = MAXKEYLEN;
+
   if (!(ep = (*kp->getcrypt) (*kp->modep)))
     {
       if (len == 0)


Trying 192.168.0.160...
Connected to 192.168.0.160.
Escape character is '^]'.

[+] Exploiting 192.168.0.160, telnetd rulez!
[+] Target OS - FreeBSD 8.2 amd64
[*] Enjoy your shell
uid=0(root) gid=0(wheel) groups=0(wheel),5(operator)
uname -a
FreeBSD ironport.example.com 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Fri Mar 14 10:49:50 PDT 2014     [email protected]:/usr/build/iproot/freebsd/mods/src/sys/amd64/compile/MESSAGING_GATEWAY.amd64  amd64

Disclosure Timeline
19-05-2014: Vendor Notification
20-05-2014: Vendor Response/Feedback
27-08-2014: Vendor Fix/Patch
22-10-2014: Public Disclosure

References:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-4862
http://www.freebsd.org/security/advisories/FreeBSD-SA-11:08.telnetd.asc
http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120126-ironport

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