cbcvebase.
CVE-2011-2039
published 2011-06-02

CVE-2011-2039: The helper application in Cisco AnyConnect Secure Mobility Client (formerly AnyConnect VPN Client) before 2.3.185 on Windows, and on Windows Mobile, downloads…

PriorityP268high7.6CVSS 2.0
AVNACHAuNCCICAC
EXPLOIT
EPSS
69.96%
99.3th percentile
The helper application in Cisco AnyConnect Secure Mobility Client (formerly AnyConnect VPN Client) before 2.3.185 on Windows, and on Windows Mobile, downloads a client executable file (vpndownloader.exe) without verifying its authenticity, which allows remote attackers to execute arbitrary code via the url property to a certain ActiveX control in vpnweb.ocx, aka Bug ID CSCsy00904.

Affected

9 ranges
VendorProductVersion rangeFixed in
ciscoanyconnect_secure_mobility
ciscoanyconnect_secure_mobility_client<= 2.3
ciscoanyconnect_secure_mobility_client
ciscoanyconnect_secure_mobility_client
ciscoanyconnect_secure_mobility_client
ciscoanyconnect_secure_mobility_client
ciscoanyconnect_secure_mobility_client
ciscoanyconnect_secure_mobility_client
ciscoanyconnect_secure_mobility_client

Detection & IOCsextracted from sources · hover to see the quote

filenamevpndownloader.exe
filenamevpnweb.ocx
otherclsid:55963676-2F5E-4BAF-AC28-CF26AA587566
filenameupdates.txt
snort
alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"ET ACTIVEX Cisco AnyConnect VPN Secure Mobility Client Cisco.AnyConnect.VPNWeb.1 Arbitrary Program Execution Attempt"; flow:established,to_client; file.data; content:"ActiveXObject"; nocase; content:"Cisco.AnyConnect.VPNWeb.1"; fast_pattern; nocase; distance:0; content:"url"; nocase; distance:0; reference:url,labs.idefense.com/intelligence/vulnerabilities/display.php?id=909; reference:bid,48081; reference:cve,2011-2039; reference:cve,2011-2040; classtype:attempted-user; sid:2012930; rev:5; metadata:created_at 2011_06_03, cve CVE_2011_2039, confidence Medium, signature_severity Unknown, updated_at 2024_04_09;)
  • Exploit HTML instantiates the ActiveX control by ProgID 'Cisco.AnyConnect.VPNWeb.1' and sets the 'url' property — detect co-occurrence of these strings in HTTP responses.
  • The ActiveX CLSID 55963676-2F5E-4BAF-AC28-CF26AA587566 (vpnweb.ocx) being instantiated via JavaScript in a browser page is a strong indicator of exploitation.
  • The exploit also requests an 'updates.txt' file from the attacker-controlled server prior to delivering the payload executable — a two-stage HTTP request pattern (updates.txt then vpndownloader.exe) from the same host is suspicious.
  • ·The Snort/ET rule (sid:2012930) also covers CVE-2011-2040 in addition to CVE-2011-2039; tune accordingly to avoid false attribution.
  • ·The exploit uses JSObfu obfuscation on the delivered HTML, so static string matching on 'Cisco.AnyConnect.VPNWeb.1' or the CLSID may be evaded by obfuscated variants — consider behavioural detection of vpndownloader.exe spawning from a browser process.
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