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Acrobat DcApplication · Adobe

CVE-2021-39863

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
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 Buffer Overflow vulnerability when parsing a specially crafted PDF file. 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.

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

Buffer overflow vulnerability in Adobe Acrobat Reader DC when parsing specially crafted PDF files. Successful exploitation allows arbitrary code execution in the context of the current user. The attack requires user interaction—the victim must open a malicious PDF file.

MitigationApply vendor-supplied security patches from Adobe for the affected versions (2021.005.20060 and earlier, 2020.004.30006 and earlier, 2017.011.30199 and earlier). Users should avoid opening PDF files from untrusted sources until patches are applied.

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
Acrobat DcApplication
Affected:>= 15.008.20082, <= 21.005.20060>= 15.008.20082, <= 21.005.20058
Acrobat Reader DcApplication
Affected:>= 15.008.20082, <= 21.005.20060
AcrobatApplication
Affected:>= 20.001.30005, <= 20.004.30006
Acrobat ReaderApplication
Affected:>= 20.001.30005, <= 20.004.30006
Acrobat 2017Application
Affected:>= 17.011.30059, <= 17.011.30199
Acrobat Reader 2017Application
Affected:>= 17.011.30059, <= 17.011.30199

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 Acrobat or Reader version
    Open the application, then go to Help > About Adobe Acrobat (or Reader). Alternatively, on Windows check the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Adobe\Adobe Acrobat\DC\Version or for 32-bit: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Adobe\Adobe Acrobat\DC\Version
    Affected if The installed version falls within any of these ranges: 15.008.20082 to 21.005.20060, 20.001.30005 to 20.004.30006, or 17.011.30059 to 17.011.30199
  2. Confirm product variant and build
    In Help > About, note whether the product is Acrobat DC, Acrobat 2020, Acrobat 2017, or Reader variant. Record the full numeric build number (for example, 21.005.20060)
    Affected if The product is Adobe Acrobat or Reader DC with build 21.005.20060 or lower, Acrobat/Reader 2020 with build 20.004.30006 or lower, or Acrobat/Reader 2017 with build 17.011.30199 or lower
  3. Verify PDF handling is enabled
    Check that the application can open PDF files by confirming the PDF file association or trying to open any PDF document. On Windows, also check the registry key HKCR\.pdf to confirm PDF file type is registered to the Adobe application
    Affected if PDF files are associated with and can be opened by the affected Adobe application version
  4. Confirm user environment permits PDF file access
    Verify the user has permissions to open PDF files through the application. This can be confirmed by attempting to open any PDF file or by checking file type associations in the operating system
    Affected if Users can open PDF files in the vulnerable Adobe application version

A user is affected if they have any version of Adobe Acrobat DC, Acrobat 2020, Acrobat 2017, or their Reader equivalents matching the build numbers 21.005.20060 or lower, 20.004.30006 or lower, or 17.011.30199 or lower respectively, and the application is capable of opening 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

Apply vendor-supplied security patches from Adobe for the affected versions (2021.005.20060 and earlier, 2020.004.30006 and earlier, 2017.011.30199 and earlier). Users should avoid opening PDF files from untrusted sources until patches are applied.

Recommended fix High confidence

Adobe Acrobat/Reader DC (2021.006 or later for version 21.x; for 2017 track, upgrade to latest 2017 release or migrate to DC track)

  1. 1. Close all Adobe Acrobat or Adobe Acrobat Reader instances that are currently running.
  2. 2. Navigate to the official Adobe download page for Acrobat or Acrobat Reader at adobe.com.
  3. 3. Download the latest version of Adobe Acrobat DC or Adobe Acrobat Reader DC (or the appropriate product for your existing installation).
  4. 4. Run the downloaded installer and follow the on-screen prompts to complete the installation.
  5. 5. After installation, verify the version by opening Adobe Acrobat/Reader and navigating to Help > About Adobe Acrobat (or About Adobe Acrobat Reader) to confirm you are on a version newer than 21.005.20060, 20.004.30006, or 17.011.30199.
  6. 6. Ensure Adobe Acrobat or Reader is set to automatically install updates via Edit > Preferences > Updater (or through the Adobe Acrobat/Reader updater settings).
Caveat Upgrading Acrobat/Reader may require reconfiguration of preferences, plugins, or integration settings; ensure compatibility with existing PDF workflows

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

Fix this in Acrobat Dc Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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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-2021-39863 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