---
id: "CVE-2021-28550"
kind: "vulnerability"
aliases: ["CVE-2021-28550"]
title: "Adobe Acrobat and Reader: Adobe Acrobat and Reader Use-After-Free Vulnerability"
severity: "critical"
cvss: 9.6
epss: 0.51851
exploited: true
status: "open"
category: "other"
products: [{"name": "Adobe Acrobat and Reader", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["adobe-acrobat", "adobe-reader", "desktop", "exploited", "macos", "other", "windows"]
not_affected_if: ["fixed-version-installed"]
published_at: "2021-09-02T17:15:08+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-28550", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2021-28550", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2021-28550", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Adobe Acrobat and Reader: Adobe Acrobat and Reader Use-After-Free Vulnerability

Adobe Acrobat and Reader contain a use-after-free memory bug that lets a crafted PDF run code as the current user. CISA lists it as actively exploited in the wild.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Adobe Acrobat and Reader affected ? fixed ?

## How to check

Open Acrobat or Reader and check Help > About to see the installed version, then compare it to the patched release in the Adobe advisory.

## Fix

Update Adobe Acrobat and Reader to the patched version named in Adobe's advisory, as CISA directs.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-28550
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2021-28550
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2021-28550

## From the sources

Acrobat Reader DC versions versions 2021.001.20150 (and earlier), 2020.001.30020 (and earlier) and 2017.011.30194 (and earlier) are affected by a Use After Free vulnerability. 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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_