ZoneAlarm TrueVector Internet Monitor service insecure NTFS permissions
vulnerability
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Yorick Koster, December 2019
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Abstract
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A vulnerability was found in the TrueVector Internet Monitor
service,
which is installed as part of the Check Point ZoneAlarm firewall.
This
vulnerability allows a local attacker to cause the affected service
to
change the file permissions of arbitrary local files. After the
file
permissions have been changed, the attacker can then overwrite
its
content, and ultimately gain elevated privileges on the
vulnerable
machine.
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Tested version
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This vulnerability was successfully verified on ZoneAlarm Free
Firewall
v15.8.023.18219/TrueVector Internet Monitor v15.8.7.18219.
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Fix
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Check Point released new versions of ZoneAlarm Firewall that fix
this
vulnerability. The latest version of ZoneAlarm Free Firewall
(v15.8.043.18324) can be obtained from
https://www.zonealarm.com/software/free-firewall/download.
The 2020-03 Cumulative Update [2] for Windows 10 adds
hardlink
mitigations. After installing this update, Windows will require
write
access on the target file otherwise the hardlink won't be
created.
Requiring write access on the target file also mitigates this
issue.
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Introduction
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A vulnerability was found in the TrueVector Internet Monitor
service,
which is installed as part of the Check Point ZoneAlarm firewall.
This
vulnerability allows a local attacker to cause the affected service
to
change the file permissions of arbitrary local files. After the
file
permissions have been changed, the attacker can then overwrite
its
content, and ultimately gain elevated privileges on the
vulnerable
machine.
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Vulnerability details
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The TrueVector Internet Monitor service is running as LocalSystem,
it
periodically creates a number of backup files within the
%ProgramData%\CheckPoint\ZoneAlarm\Data\ folder. When these files
are
created, their file permissions are explicitly set to Full Control
for
Authenticated Users. A local attacker can create a hardlink with
the
same name as the backup files, causing the permissions of another
file
to be changed.
After the file permissions have been changed, the attacker can
then
overwrite its content, and ultimately gain elevated privileges on
the
vulnerable machine. Hardlinks can be created using James Forshaw's
[3]
CreateHardlink [4] tool.
CreateHardlink.exe
"%ProgramData%\CheckPoint\ZoneAlarm\Data\bu_tosave.ndb"
"%SystemRoot%\win.ini"
CreateHardlink.exe
"%ProgramData%\CheckPoint\ZoneAlarm\Data\bu_todelete.ndb"
"%SystemRoot%\win.ini"
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References
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[1]
https://www.securify.nl/advisory/SFY20200317/zonealarm-truevector-internet-monitor-service-insecure-ntfs-permissions-vulnerability.html
[2]
https://www.catalog.update.microsoft.com/Search.aspx?q=KB4540673
[3] https://twitter.com/tiraniddo
[4]
https://github.com/googleprojectzero/symboliclink-testing-tools/tree/master/CreateHardlink
