Microsoft Windows 7/10 cmd.exe ASCII Substitute Character privileges management
|CVSS Meta Temp Score|
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|Current Exploit Price (≈)|
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|CTI Interest Score|
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A vulnerability, which was classified as critical, has been found in Microsoft Windows 7/10 (Operating System). Affected by this issue is an unknown code block of the file cmd.exe. The manipulation as part of a ASCII Substitute Character leads to a privilege escalation vulnerability. Using CWE to declare the problem leads to CWE-269. Impacted is confidentiality, integrity, and availability.
The weakness was disclosed 11/11/2016 by Julian Horoszkiewicz as Unexpected behavior of cmd.exe while processing .bat files leads to potential command injection vulnerabilities as not defined mailinglist post (Full-Disclosure). The advisory is available at seclists.org. The vendor was not involved in the coordination of the public release. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details as well as a public exploit are known. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 07/07/2019). The advisory points out:
It was discovered that cmd.exe, when processing .bat files, treats the ASCII substitute character (code 26) as a command separator (like & or |). This opens the way for unexpected command injection vulnerabilities in applications which generate .bat files based on user input, as this character is not filtered by most application input sanitisers against command injection.
A public exploit has been developed by Julian Horoszkiewicz in HTTP POST Request and been published immediately after the advisory. It is declared as proof-of-concept. The exploit is available at seclists.org. As 0-day the estimated underground price was around $25k-$100k. The code used by the exploit is:
POST /escape_shell_cmd.php HTTP/1.1 Host: localhost User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:47.0) Gecko/20100101 Firefox/47.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: pl,en-US;q=0.7,en;q=0.3 Accept-Encoding: gzip, deflate Connection: close Content-Type: application/x-www-form-urlencoded Content-Length: 35 dir=.%1anet user /add hacked hackedThe advisory illustrates:
Let's send a request containing "." as a parameter to the hardcoded "dir" command, appended with another command - taking advantage of %1a as a command separator.
There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.
CVSSv3VulDB Meta Base Score: 7.3
VulDB Meta Temp Score: 6.6
VulDB Base Score: 7.3
VulDB Temp Score: 6.6
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ExploitingClass: Privilege escalation
Author: Julian Horoszkiewicz
Programming Language: 🔍
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Threat IntelligenceInterest: 🔍
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CountermeasuresRecommended: no mitigation known
0-Day Time: 🔍
Exploit Delay Time: 🔍
11/11/2016 +0 days 🔍
11/14/2016 +3 days 🔍
07/07/2019 +965 days 🔍
Advisory: Unexpected behavior of cmd.exe while processing .bat files leads to potential command injection vulnerabilities
Researcher: Julian Horoszkiewicz
Status: Not defined
scip Labs: https://www.scip.ch/en/?labs.20161215
EntryCreated: 11/14/2016 09:04 AM
Updated: 07/07/2019 06:35 PM
Changes: (2) software_type vulnerability_cwe
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