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zdtGoogle Security Research1337DAY-ID-31831
HistoryDec 22, 2018 - 12:00 a.m.

VBScript - MSXML Execution Policy Bypass Exploit

2018-12-2200:00:00
Google Security Research
0day.today
47

7.5 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

7.6 High

CVSS2

Access Vector

NETWORK

Access Complexity

HIGH

Authentication

NONE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

AV:N/AC:H/Au:N/C:C/I:C/A:C

0.255 Low

EPSS

Percentile

96.2%

According to https://blogs.windows.com/msedgedev/2017/07/07/update-disabling-vbscript-internet-explorer-11/, Starting from Windows 10 Fall Creators Update, VBScript execution in IE 11 should be disabled for websites in the Internet Zone and the Restricted Sites Zone by default.

However, the VBScript execution policy does not appear to cover VBScript code in MSXML xsl files which can still execute VBScript, even when loaded from the Internet Zone.

To demonstrate, place the files in the attached archive on a web server in the Internet zone and open index.html. If successful, the text "Hello from VBscript" will be rendered on the page. If you look at the provided code, this text is assembled dynamically by VBScript.

This has been tested on Windows 10 Version 1803 with the latest patches applied and VBScript execution policy applied for the Internet Zone (HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3\140C = 3).


Proof of Concept:
https://github.com/offensive-security/exploitdb-bin-sploits/raw/master/bin-sploits/46023.zip

7.5 High

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

REQUIRED

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

HIGH

CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H

7.6 High

CVSS2

Access Vector

NETWORK

Access Complexity

HIGH

Authentication

NONE

Confidentiality Impact

COMPLETE

Integrity Impact

COMPLETE

Availability Impact

COMPLETE

AV:N/AC:H/Au:N/C:C/I:C/A:C

0.255 Low

EPSS

Percentile

96.2%