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AcrobatApplication · Adobe

CVE-2021-39836

HIGH · 7.8 CVSS v3.1 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 buttonGetIcon 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 buttonGetIcon action processing. When a user opens a maliciously crafted PDF file, the vulnerability allows an attacker to free memory prematurely and then reuse the freed memory pointer, potentially leading to arbitrary code execution with the privileges of the current user.

MitigationUpdate Adobe Acrobat Reader DC to a version newer than 2021.005.20060, 2020.004.30006, or 2017.011.30199 as appropriate. Until patches are applied, exercise caution when opening PDF files from untrusted sources.

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:>= 17.011.30059, <= 17.011.30199>= 20.001.30005, <= 20.004.30006
Acrobat ReaderApplication
Affected:>= 17.011.30059, <= 17.011.30199>= 20.001.30005, <= 20.004.30006
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:3.1/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. Identify installed Adobe product and version
    On Windows, open the application and go to Help > About Adobe Acrobat/Reader, or check the registry key HKLM\SOFTWARE\Adobe\Acrobat\DC\Version (for Acrobat/Reader DC). On macOS, right-click the app in /Applications and select Get Info, or check the Info.plist file inside the application bundle.
    Affected if The version number falls within any of the affected ranges: 17.011.30059 to 17.011.30199, 20.001.30005 to 20.004.30006, 15.008.20082 to 21.005.20058, or 15.008.20082 to 21.005.20060.
  2. Confirm product type
    Verify whether the installed product is Adobe Acrobat or Adobe Acrobat Reader. The affected version ranges differ slightly between the two product lines, so confirm which product is installed before comparing against the ranges.
    Affected if The product is Adobe Acrobat or Adobe Acrobat Reader and the version matches an affected range.
  3. Check for AcroForm usage
    This vulnerability is triggered specifically when processing AcroForm buttonGetIcon actions within PDF files. The vulnerability exists in the PDF rendering engine when handling icon actions in form buttons. To be vulnerable, the software must be capable of rendering PDF files with AcroForm fields.
    Affected if The installed version is in the affected range and the software can render or process PDF files with AcroForm fields enabled (this is default behavior for Reader/Acrobat).

A user is affected if their installed Adobe Acrobat or Adobe Acrobat Reader version falls within any of the specified affected version ranges and they open PDF files.

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 a version newer than 2021.005.20060, 2020.004.30006, or 2017.011.30199 as appropriate. Until patches are applied, exercise caution when opening PDF files from untrusted sources.

Recommended fix High confidence

Acrobat/Acrobat Reader 2021.006 or later; 2020.004.30007 or later; 2017.011.30200 or later

  1. 1. Open Adobe Acrobat or Acrobat Reader
  2. 2. Navigate to Help > Check for Updates or use the built-in update mechanism
  3. 3. Alternatively, download the latest version from the official Adobe website: https://get.adobe.com/reader/ (for Reader) or https://get.adobe.com/acrobat/ (for Acrobat)
  4. 4. Install the latest version which contains the security patch for CVE-2021-39836
  5. 5. Restart the application after updating
  6. 6. Verify the version number matches a patched release (2021.006.x or later for 2021 track; 2020.004.30007 or later for 2020 track; 2017.011.30200 or later for 2017 track)
Caveat Standard minor version upgrade - review Adobe release notes for any feature changes specific to your version track

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

Fix this in Acrobat Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2021-39836 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