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Acrobat DcApplication · Adobe

CVE-2021-40726

HIGH · 7.8 CVSS v3.0 Published 2021-10-07
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 use-after-free vulnerability when processing AcroForm field that could result in arbitrary code execution in the context of the current user. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or 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 when processing AcroForm fields. The vulnerability allows an attacker to free memory and then access it after it's been freed, potentially achieving arbitrary code execution. Exploitation requires user interaction - either opening a malicious PDF file or visiting a malicious webpage that triggers the vulnerable code path.

MitigationUpdate Adobe Acrobat Reader DC to the latest version (2021.006.20060 or later for the 2021 track, 2020.004.30007 or later for the 2020 track, 2017.011.30200 or later for the 2017 track). Avoid opening untrusted PDF files or visiting untrusted websites until the update is 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:>= 17.011.30059, <= 17.011.30199>= 20.001.30005, <= 20.004.30006>= 15.008.20082, <= 21.005.20058>= 15.008.20082, <= 21.005.20060
Acrobat Reader DcApplication
Affected:>= 17.011.30059, <= 17.011.30199>= 20.001.30005, <= 20.004.30006>= 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. Check installed Adobe Acrobat Reader DC version
    Open Adobe Acrobat Reader DC and navigate to Help > About Adobe Acrobat Reader DC, or view the program in Windows Programs and Features. Note the full version number and build (for example, 21.005.20059).
    Affected if The version number falls within any of these 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. Verify AcroForm processing is enabled
    In Adobe Acrobat Reader DC, go to Edit > Preferences > Forms and confirm that AcroForm handling is enabled. This is typically enabled by default.
    Affected if AcroForm processing is enabled, which is the default state and required for the vulnerable code path to be reached.
  3. Check for recent PDF usage
    Review recently opened PDF files or check the application file history to identify if untrusted or malicious PDF files may have been opened.
    Affected if The user has opened PDF files from untrusted sources, which is required for exploitation along with the vulnerable version.

The environment is affected if Adobe Acrobat Reader DC version falls within the specified version ranges and AcroForm processing is enabled, since exploitation requires both the vulnerable version and user interaction with a malicious PDF.

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 version (2021.006.20060 or later for the 2021 track, 2020.004.30007 or later for the 2020 track, 2017.011.30200 or later for the 2017 track). Avoid opening untrusted PDF files or visiting untrusted websites until the update is applied.

Recommended fix High confidence

Adobe Acrobat Reader DC / Acrobat DC versions 2021.006.20030 or later for 2021 track; 2020.004.30007 or later for 2020 track; 2017.011.30200 or later for 2017 track

  1. 1. Verify the current Adobe Acrobat or Acrobat Reader version by navigating to Help > About Adobe Acrobat Reader DC (or About Adobe Acrobat DC)
  2. 2. Close all Adobe applications completely
  3. 3. Download the latest version from the official Adobe website at https://get.adobe.com/reader/ (for Reader) or https://get.adobe.com/acrobat/ (for Acrobat Pro)
  4. 4. Run the installer and follow the prompts to complete the upgrade
  5. 5. After installation, restart the computer and verify the new version by checking Help > About
Caveat Standard Adobe update - minimal risk; however, always backup critical documents before performing software updates

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

Fix this in Acrobat Dc Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
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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-2021-40726 in production — separate from our analysis above.

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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