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AcrobatApplication · Adobe

CVE-2021-39837

HIGH · 7.8 CVSS v3.0 Published 2021-09-29
Fix available
A fix is available. Upgrade to after 21.005.20060 or later.
See remediation →
81/100
Remediation priority · High
High EPSS No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Acrobat Reader DC versions 2021.005.20060 (and earlier), 2020.004.30006 (and earlier) and 2017.011.30199 (and earlier) are affected by a use-after-free vulnerability in the processing of the AcroForm deleteItemAt action that could result in 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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A use-after-free vulnerability exists in Adobe Acrobat Reader DC's AcroForm processing, specifically in the deleteItemAt action. This memory corruption flaw allows arbitrary code execution in the context of the current user when a victim opens a maliciously crafted PDF file.

MitigationUpdate Adobe Acrobat Reader DC to the latest patched version. Instruct users to avoid opening untrusted or unexpected PDF files, as exploitation requires user interaction.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AcrobatApplication
Affected:>= 20.001.30005, <= 20.004.30006>= 17.011.30059, <= 17.011.30199
Acrobat ReaderApplication
Affected:>= 20.001.30005, <= 20.004.30006>= 17.011.30059, <= 17.011.30199
Acrobat DcApplication
Affected:>= 15.008.20082, <= 21.005.20058>= 15.008.20082, <= 21.005.20060
Acrobat Reader DcApplication
Affected:>= 15.008.20082, <= 21.005.20058>= 15.008.20082, <= 21.005.20060

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Adobe Acrobat or Reader is installed
    Check for the application in Windows via Registry key HKLM\SOFTWARE\Adobe or by looking in C:\Program Files\Adobe or C:\Program Files (x86)\Adobe. On Mac, check /Applications for Adobe Acrobat or Adobe Acrobat Reader.
    Affected if Either Adobe Acrobat or Adobe Acrobat Reader DC is found on the system.
  2. Identify the exact installed version
    Open Adobe Acrobat/Reader, then go to Help > About to view the precise version number. Alternatively on Windows, check the registry key HKLM\SOFTWARE\Adobe\Acrobat\DC\Version or HKLM\SOFTWARE\Adobe\Acrobat Reader\DC\Version. On Mac, right-click the app in Applications and select Get Info.
    Affected if A version number is retrieved.
  3. Compare version against affected ranges
    Match your installed version against: Acrobat/Reader 20.x between 20.001.30005 and 20.004.30006; Acrobat/Reader 17.x between 17.011.30059 and 17.011.30199; Acrobat/Reader DC versions 15.008.20082 through 21.005.20058 or 21.005.20060.
    Affected if The installed version falls within ANY of these ranges: 20.001.30005-20.004.30006, 17.011.30059-17.011.30199, 15.008.20082-21.005.20058, or 15.008.20082-21.005.20060.
  4. Verify AcroForm processing is available
    Open any PDF file in the installed Adobe application and check if Forms functionality is accessible via Tools > Prepare Form, or check if the application can open PDFs containing form fields. This feature is built into standard installations.
    Affected if AcroForm processing capability is present in the installation.

The system is affected if Adobe Acrobat or Acrobat Reader DC is installed AND its version falls within the listed vulnerable ranges AND AcroForm processing is available, which it is by default in standard installations.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 21.005.20060
Interim mitigation

Update Adobe Acrobat Reader DC to the latest patched version. Instruct users to avoid opening untrusted or unexpected PDF files, as exploitation requires user interaction.

Recommended fix High confidence

2021.005.20061 or later (2021 track), 2020.004.30007 or later (2020 track), 2017.011.30200 or later (2017 track)

  1. 1. Identify the currently installed Adobe Acrobat or Reader version from the application (Help > About Adobe Acrobat/Reader)
  2. 2. Determine which product track (Classic/2017, 2020, or 2021) and version is installed
  3. 3. Download the appropriate fixed version from the official Adobe download page at get.adobe.com/reader or helpx.adobe.com/acrobat/release-note.html
  4. 4. Close all instances of Adobe Acrobat or Reader
  5. 5. Run the installer for the fixed version (2021.005.20061 or later for 2021 track, 2020.004.30007 or later for 2020 track, 2017.011.30200 or later for 2017 track)
  6. 6. Follow the installation wizard prompts to complete the update
  7. 7. Verify the installed version after update by checking Help > About to confirm the version is beyond the affected range
  8. 8. Ensure Adobe Auto-Update is enabled to receive future security patches
Caveat Upgrading may change the user interface or remove support for older PDF features; review Adobe release notes for any functionality changes in the new version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Acrobat Scoped from the published advisory
  • Consultation1.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
4.0 hours of engineering $750
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-39837 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data