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TippingPoint IPS Signature Evasion
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SUMMARY
During security analysis of the Tippingpoint IPS product a signature
evasion vulnerability was discovered. The use of specific Unicode
characters on particular web servers allows a remote user to bypass IPS
detection.
DETAILS
Vulnerable Systems:
* TippingPoint IPS running TOS version 2.1
* TippingPoint IPS running TOS version 2.2.0 up to and including 2.2.4
By using a hex encoded alternate Unicode character for forward slash (/) a
request can be produced that will not match any IPS signature present in
the TippingPoint device.
Example:
http://www.test.com/scripts/cmd.exe is a known attack, and detected by a
signature.
The same URI with alternate Unicode forward slash characters are not
detected by the signature.
http://www.test.com/scripts%c0%afcmd.exe
http://www.test.com/scripts%e0%80%afcmd.exe
http://www.test.com/scripts%c1%9ccmd.exe
Web servers located behind a Tippingpoint IPS device which are capable of
decoding alternate Unicode characters can be accessed, and exploited
without triggering the IPS device.
Solutions:
Security-Assessment.com has been in contact with Tipping and a new version
of the Tippingpoint IPS software has been released to address the
discovered vulnerability:
<http://www.3com.com/securityalert/alerts/3COM-07-003.html>
http://www.3com.com/securityalert/alerts/3COM-07-003.html
This issue has been addressed in various TOS releases as indicated by the
affected product below.
- X-Family devices, 2.5.0.6682.
- non-X-Family device (not including 600E, 1200E, 2400E or 5000E),
2.5.1.6826.
- non-X-Family device (including 600E, 1200E, 2400E or 5000E),
2.5.2.6919.
ADDITIONAL INFORMATION
The information has been provided by
<mailto:paul.craig@security-assessment.com> Paul Craig.
The original article can be found at:
<http://security-assessment.com/files/advisories/2007-07-11_Tippingpoint_IPS_Signature_Evasion.pdf>
http://security-assessment.com/files/advisories/2007-07-11_Tippingpoint_IPS_Signature_Evasion.pdf
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