CVE-2021-39863

HIGH

Adobe Acrobat and Reader DC < 21.005.20060 - Heap-based Buffer Overflow via Crafted PDF File

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 2 public exploits for CVE-2021-39863. PoCs published by lsw29475, WHS-SEGFAULT.

AI-analyzed exploit summary This is a functional exploit PoC for CVE-2021-39863, leveraging a use-after-free vulnerability in Adobe Acrobat Reader to achieve arbitrary memory read/write and execute shellcode. The exploit uses heap spraying and ArrayBuffer manipulation to corrupt memory and hijack execution flow.

Description

Acrobat Reader DC versions 2021.005.20060 (and earlier), 2020.004.30006 (and earlier) and 2017.011.30199 (and earlier) are affected by a Buffer Overflow vulnerability when parsing a specially crafted PDF file. An unauthenticated attacker could leverage this vulnerability to achieve arbitrary code execution in the context of the current user. Exploitation of this issue requires user interaction in that a victim must open a malicious file.

Exploits (2)

nomisec WORKING POC 2 stars
by lsw29475 · poc
https://github.com/lsw29475/CVE-2021-39863

This is a functional exploit PoC for CVE-2021-39863, leveraging a use-after-free vulnerability in Adobe Acrobat Reader to achieve arbitrary memory read/write and execute shellcode. The exploit uses heap spraying and ArrayBuffer manipulation to corrupt memory and hijack execution flow.

Classification
Working Poc 95%
Attack Type
Rce
Complexity
Complex
Reliability
Racy
Target: Adobe Acrobat Reader DC (versions prior to 21.007.20099)
No auth needed
Prerequisites: Victim must open a malicious PDF file in a vulnerable version of Adobe Acrobat Reader
devstral-2 · analyzed Feb 19, 2026 Full analysis →
nomisec WORKING POC
by WHS-SEGFAULT · poc
https://github.com/WHS-SEGFAULT/CVE-2021-39863

The repository contains a functional exploit for CVE-2021-39863, demonstrating a heap-based buffer overflow vulnerability in the URL parsing logic of a target software. The exploit manipulates URL concatenation to trigger memory corruption, potentially leading to remote code execution.

Classification
Working Poc 90%
Attack Type
Rce
Complexity
Moderate
Reliability
Reliable
Target: Unknown (likely a web server or URL parsing library)
No auth needed
Prerequisites: Network access to the vulnerable service
devstral-2 · analyzed Feb 19, 2026 Full analysis →

References (1)

Core 1
Core References
Release Notes, Vendor Advisory x_refsource_misc
https://helpx.adobe.com/security/products/acrobat/apsb21-55.html

Scores

CVSS v3 7.8
EPSS 0.1250
EPSS Percentile 95.7%
Attack Vector LOCAL
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Details

CWE
CWE-122
Status published
Products (6)
adobe/acrobat 20.001.30005 - 20.004.30006
adobe/acrobat_2017 17.011.30059 - 17.011.30199
adobe/acrobat_dc 15.008.20082 - 21.005.20060
adobe/acrobat_reader 20.001.30005 - 20.004.30006
adobe/acrobat_reader_2017 17.011.30059 - 17.011.30199
adobe/acrobat_reader_dc 15.008.20082 - 21.005.20060
Published Sep 29, 2021
Tracked Since Feb 18, 2026