The Cisco SSLVPN feature provides remote access to enterprise sites by users from anywhere on the Internet. The SSLVPN provides users with secure access to specific enterprise applications, such as e-mail and web browsing, without requiring them to have VPN client software installed on their end-user devices.
The WebVPN Enhancements feature (Cisco IOS SSLVPN), released in Cisco IOS Release 12.4(6)T, obsoletes the commands and configurations originally put forward in Cisco IOS WebVPN.
Further information about Cisco IOS WebVPN is available in the "Cisco IOS Software Release 12.3T WebVPN feature guide" at the following link: http://www.cisco.com/en/US/docs/ios/12_3t/12_3t14/feature/guide/g_sslvpn.html
Further information about Cisco IOS SSLVPN is available in the "Cisco IOS Software Release 12.4T SSLVPN feature guide" at the following link: http://www.cisco.com/en/US/docs/ios/12_4t/12_4t11/htwebvpn.html
Details regarding these two vulnerabilities in Cisco IOS devices that are running affected versions of system software are:
Crafted HTTPS packet will crash device
A device configured for SSLVPN may reload or hang when it receives a specially crafted HTTPS packet. Completion of the 3-way handshake to the associated TCP port number of the SSLVPN feature is required in order for the vulnerability to be successfully exploited, however authentication is "not" required. The default TCP port number for SSLVPN is 443.
This vulnerability is documented in Cisco bug ID CSCsk62253 (registered customers only) and Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-0626 has been assigned to this vulnerability.
SSLVPN sessions cause a memory leak in the device
A device configured for SSLVPN may leak transmission control blocks (TCBs) when processing an abnormally disconnected SSL session. Continued exploitation may result in the device depleting its memory resources and result in a crash of the device. Authentication is "not" required to exploit this vulnerability.
The memory leak can be detected by running the command "show tcp brief", like in the following example:
Router#show tcp brief
TCB Local Address Foreign Address (state)
468BBDC0 192.168.0.22.443 192.168.0.33.19794 CLOSEWAIT
482D4730 192.168.0.22.443 192.168.0.33.22092 CLOSEWAIT
482779A4 192.168.0.22.443 192.168.0.33.16978 CLOSEWAIT
4693DEBC 192.168.0.22.443 192.168.0.33.21580 CLOSEWAIT
482D3418 192.168.0.22.443 192.168.0.33.17244 CLOSEWAIT
482B8ACC 192.168.0.22.443 192.168.0.33.16564 CLOSEWAIT
46954EB0 192.168.0.22.443 192.168.0.33.19532 CLOSEWAIT
468BA9B8 192.168.0.22.443 192.168.0.33.15781 CLOSEWAIT
482908C4 192.168.0.22.443 192.168.0.33.19275 CLOSEWAIT
4829D66C 192.168.0.22.443 192.168.0.33.19314 CLOSEWAIT
468A2D94 192.168.0.22.443 192.168.0.33.14736 CLOSEWAIT
4688F590 192.168.0.22.443 192.168.0.33.18786 CLOSEWAIT
4693CBA4 192.168.0.22.443 192.168.0.33.12176 CLOSEWAIT
4829ABC4 192.168.0.22.443 192.168.0.33.39629 CLOSEWAIT
4691206C 192.168.0.22.443 192.168.0.33.17818 CLOSEWAIT
46868224 192.168.0.22.443 192.168.0.33.16774 CLOSEWAIT
4832BFAC 192.168.0.22.443 192.168.0.33.39883 CLOSEWAIT
482D10CC 192.168.0.22.443 192.168.0.33.13677 CLOSEWAIT
4829B120 192.168.0.22.443 192.168.0.33.20870 CLOSEWAIT
482862FC 192.168.0.22.443 192.168.0.33.17035 CLOSEWAIT
482EC13C 192.168.0.22.443 192.168.0.33.16053 CLOSEWAIT
482901D8 192.168.0.22.443 192.168.0.33.16200 CLOSEWAIT
In the output above, those Transmission Control Blocks (TCBs) in the state CLOSEWAIT will not go away and represent memory leaks. Please note that only TCP connections with a local TCP port of 443 (the well-known port for HTTPS) are relevant.
This vulnerability is documented in Cisco bug ID CSCsw24700 (registered customers only) and Common Vulnerabilities and Exposures (CVE) identifier CVE-2009-0628 has been assigned to this vulnerability.