CVE-2021-39839
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 · uneditedAcrobat 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 getItem 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 · moderate confidenceA use-after-free vulnerability in Adobe Acrobat Reader DC's AcroForm getItem action allows memory that has been freed to be accessed, potentially enabling arbitrary code execution in the current user's context when a victim opens a specially crafted malicious PDF file.
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>= 20.001.30005, <= 20.004.30006>= 17.011.30059, <= 17.011.30199>= 20.001.30005, <= 20.004.30006>= 17.011.30059, <= 17.011.30199>= 15.008.20082, <= 21.005.20058>= 15.008.20082, <= 21.005.20060>= 15.008.20082, <= 21.005.20058>= 15.008.20082, <= 21.005.20060CVSS 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 checksWork through these to decide whether this CVE applies to you.
-
Identify installed Adobe Acrobat or Reader productCheck the Windows registry under HKLM\SOFTWARE\Adobe\Adobe Acrobat or HKLM\SOFTWARE\Adobe\Adobe Acrobat Reader, or on macOS check /Applications for Adobe Acrobat or Adobe Acrobat ReaderAffected if The product is not found (not installed means not affected)
-
Determine the installed version numberIn Windows, use Help > About Adobe Acrobat/Reader, or check the registry key Version in the product's registry folder. On macOS, right-click the app and select Get Info to see the version.Affected if Version cannot be determined (cannot assess if affected)
-
Compare your version against affected rangesMatch your installed version against: Acrobat/Reader 2021: 20.001.30005 through 20.004.30006; Acrobat/Reader 2017: 17.011.30059 through 17.011.30199; Acrobat/Reader DC Continuous: 15.008.20082 through 21.005.20058 or 21.005.20060 (depending on track)Affected if Your version falls within any of these ranges: 20.001.30005-20.004.30006, 17.011.30059-17.011.30199, or 15.008.20082-21.005.20058/21.005.20060
-
Verify AcroForm functionality is accessibleOpen Acrobat/Reader preferences and check if AcroForm forms are enabled, or attempt to open a PDF with AcroForm fields to confirm the feature is functionalAffected if AcroForms are disabled at the application level (the vulnerable code path may not be exercised)
-
Confirm PDF handling from untrusted sources is possibleReview whether the application allows opening PDF files from external or untrusted sources without strict policy restrictionsAffected if Users can open arbitrary PDF attachments without policy controls (exposure to malicious PDFs is possible)
Your environment is affected if Adobe Acrobat or Acrobat Reader DC is installed with a version number matching any of the specified vulnerable ranges and users can open PDF files containing AcroForm content.
Generated from the published advisory. Verify against your own configuration.
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 · scopedApply the vendor security update to Adobe Acrobat Reader DC (2021.006.20060 or later for the 2021 track, 2021.006.20060 for 2020.x, or 2017.011.30200 or later for 2017.x). Additionally, enforce policies to prevent users from opening untrusted PDF attachments or files.
Latest Adobe Acrobat Reader DC or Adobe Acrobat 2021 release (beyond 2021.005.20060)
- 1. Verify current Adobe Acrobat or Adobe Acrobat Reader DC version by navigating to Help > About Adobe Acrobat Reader DC (or About Adobe Acrobat)
- 2. Download the latest version of Adobe Acrobat Reader DC or Adobe Acrobat from the official Adobe website at get.adobe.com/reader or adobe.com
- 3. Close all running instances of Adobe Acrobat or Adobe Acrobat Reader
- 4. Run the installer and follow the on-screen prompts to complete the installation
- 5. Restart the application after installation completes
- 6. Verify the installed version is newer than 2021.005.20060 for the 2021 track, newer than 2020.004.30006 for the 2020 track, or newer than 2017.011.30199 for the 2017 track
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,744.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39839 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-39839 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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