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TITLE:
Juniper Netscreen IPSec VPN Username Enumeration Weakness

SECUNIA ADVISORY ID:
SA16474

VERIFY ADVISORY:
http://secunia.com/advisories/16474/

CRITICAL:
Not critical

IMPACT:
Exposure of system information

WHERE:
>From remote

OPERATING SYSTEM:
NetScreen ScreenOS 5.x
http://secunia.com/product/2569/
NetScreen ScreenOS 4.x
http://secunia.com/product/695/
NetScreen ScreenOS 3.x
http://secunia.com/product/798/
NetScreen ScreenOS 2.x
http://secunia.com/product/1395/

DESCRIPTION:
NTA Monitor has reported a weakness in Juniper Netscreen VPN, which
can be exploited by malicious people to gain knowledge of certain
information.

The weakness is caused due to the device returning different
responses depending on whether or not a valid username is supplied.
This can be exploited to enumerate valid usernames, which can be used
to obtain password hashes.

Successful exploitation requires that the device is configured to use
IKE aggressive mode with pre-shared key authentication.

The weakness has been reported in ScreenOS software versions up to
5.2.0.

SOLUTION:
Use certificate authentication instead of pre-shared key
authentication.

PROVIDED AND/OR DISCOVERED BY:
NTA Monitor

ORIGINAL ADVISORY:
NTA Monitor:
http://www.nta-monitor.com/news/vpn-flaws/juniper/netscreen/index.htm

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About:
This Advisory was delivered by Secunia as a free service to help
everybody keeping their systems up to date against the latest
vulnerabilities.

Subscribe:
http://secunia.com/secunia_security_advisories/

Definitions: (Criticality, Where etc.)
http://secunia.com/about_secunia_advisories/


Please Note:
Secunia recommends that you verify all advisories you receive by
clicking the link.
Secunia NEVER sends attached files with advisories.
Secunia does not advise people to install third party patches, only
use those supplied by the vendor.

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