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Acrobat DcApplication · Adobe

CVE-2021-28631

HIGH · 7.8 CVSS v3.1 Published 2021-08-24
Fix available
A fix is available. Upgrade to after 21.001.20155 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 versions 2021.001.20155 (and earlier), 2020.001.30025 (and earlier) and 2017.011.30196 (and earlier) are affected by an Use After Free vulnerability. 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 · moderate confidence

Adobe Acrobat Reader DC contains a Use After Free vulnerability where a malicious PDF file can trigger free memory being reused, allowing an attacker to achieve arbitrary code execution in the context of the current user. The attack requires user interaction to open the crafted PDF.

MitigationApply Adobe's security patches for the affected versions (2021.001.20155 and earlier, 2020.001.30025 and earlier, 2017.011.30196 and earlier). Until patched, instruct users to avoid opening untrusted PDF files.

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, <= 21.001.20155
Acrobat Reader DcApplication
Affected:>= 15.008.20082, <= 21.001.20155
AcrobatApplication
Affected:>= 17.011.30180, <= 17.011.30196>= 20.001.30005, <= 20.001.30025
Acrobat ReaderApplication
Affected:>= 17.011.30180, <= 17.011.30196>= 20.001.30005, <= 20.001.30025

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 product
    Open the application, then go to Help > About Adobe Acrobat Reader (or About Adobe Acrobat). Alternatively, on Windows check the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Adobe\Acrobat\DC\InstallVersion, or on macOS right-click the application in Applications and select Get Info.
    Affected if The product name shown is Adobe Acrobat DC, Adobe Acrobat Reader DC, Adobe Acrobat, or Adobe Acrobat Reader.
  2. Determine the exact installed version number
    Note the version string displayed in the About dialog (for example, 21.001.20155) or retrieve it from the registry value (InstallVersion\Version key on Windows, or the CFBundleShortVersionString on macOS).
    Affected if A version number is retrieved from the application.
  3. Compare the installed version against affected ranges
    Check if the version falls within any of these ranges: 15.008.20082 through 21.001.20155 for DC products; 17.011.30180 through 17.011.30196 or 20.001.30005 through 20.001.30025 for Acrobat/Reader 2017 and 2020.
    Affected if The installed version is greater than or equal to 15.008.20082 and less than or equal to 21.001.20155, OR falls within 17.011.30180-17.011.30196, OR falls within 20.001.30005-20.001.30025.
  4. Confirm PDF handling capability is enabled
    Verify the application can open and render PDF files by attempting to open any PDF document or checking that the PDF shell integration is registered with the operating system.
    Affected if The application is configured as the default handler for PDF files or users routinely open PDFs with this application.

The environment is affected if Adobe Acrobat or Adobe Acrobat Reader is installed with a version number within the vulnerable ranges listed above and the application is used to 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 21.001.20155
Interim mitigation

Apply Adobe's security patches for the affected versions (2021.001.20155 and earlier, 2020.001.30025 and earlier, 2017.011.30196 and earlier). Until patched, instruct users to avoid opening untrusted PDF files.

Recommended fix High confidence

Adobe Acrobat/Reader DC versions 2021.001.20156+, 2020.001.30026+, or 2017.011.30197+ (depending on which track is in use)

  1. 1. Identify the currently installed Adobe Acrobat or Acrobat Reader version by opening the application, selecting 'Help' > 'About Adobe Acrobat Reader' (or similar menu item)
  2. 2. For Adobe Acrobat Reader DC: If version is 2021.001.20155 or earlier, upgrade to 2021.001.20156 or later; if version is 2020.001.30025 or earlier, upgrade to 2020.001.30026 or later; if version is 2017.011.30196 or earlier, upgrade to 2017.011.30197 or later
  3. 3. For Adobe Acrobat DC (Classic track): Apply the same version guidance as Reader DC
  4. 4. Download the fixed version from the official Adobe website at helpx.adobe.com
  5. 5. Close all Adobe applications before installing the update
  6. 6. Run the installer and follow the prompts to complete the upgrade
  7. 7. After installation, verify the new version by checking 'Help' > 'About' to confirm the update was successful
Caveat Standard minor version upgrades within the same major release typically have minimal compatibility risks; ensure user documents are backed up before any software update

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
  • Implementation6.0 h
  • Testing3.0 h
  • Review / QA2.0 h
14.0 hours of engineering $2,490
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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-2021-28631 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