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CVE-2021-21086 is an out-of-bounds write vulnerability in the CoolType library of Adobe Acrobat Reader DC, affecting versions 2020.013.20074 and earlier, 2020.001.30018 and earlier, and 2017.011.30188 and earlier. The vulnerability can be triggered when a user opens a specially crafted malicious file, allowing an unauthenticated attacker to write outside the bounds of allocated memory. This can result in arbitrary code execution within the context of the current user.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository provides a working exploit for CVE-2021-21086, a vulnerability in Adobe Acrobat Reader DC (2020.013.20074 and earlier) on Windows 10. The exploit consists of two main Python scripts: 1. `generate_exploit_charstring.py`: Generates a malicious 'charstring' payload that leverages a vulnerability in the font handling (CoolType) of Adobe Reader. The script models the stack and transient array of the interpreter, crafts a charstring that triggers the vulnerability, and appends shellcode (default: launches calc.exe) to the payload. The output is a binary file named 'charstring'. 2. `charstring2pdf.py`: Embeds the generated 'charstring' into a specially crafted PDF file. This script constructs a PDF with a custom font object, encrypts the charstring, and writes the final malicious PDF ('exploit.pdf'). The README provides usage instructions: generate the charstring, embed it into a PDF, and open the PDF with a vulnerable version of Adobe Reader DC (with the sandbox disabled) to achieve code execution. The exploit is operational and can be weaponized by replacing the shellcode. No network endpoints are involved; the attack vector is a malicious file (PDF).
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