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Acrobat DcApplication · Adobe

CVE-2021-39861

MEDIUM · 5.5 CVSS v3.1 Published 2021-09-29
Fix available
A fix is available. Upgrade to after 21.005.20060 or later.
See remediation →
58/100
Remediation priority · Elevated
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 an out-of-bounds read vulnerability that could lead to disclosure of arbitrary memory information 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

Adobe Acrobat Reader DC contains an out-of-bounds read vulnerability allowing disclosure of arbitrary memory information. Exploitation requires a user to open a malicious PDF file, and the vulnerability affects versions 2021.005.20060 and earlier, 2020.004.30006 and earlier, and 2017.011.30199 and earlier.

MitigationUpdate Adobe Acrobat Reader DC to the latest patched version provided by Adobe. Until patched, avoid 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
Acrobat DcApplication
Affected:>= 20.006.20034, <= 21.005.20060>= 20.006.20034, <= 21.005.20058
Acrobat Reader DcApplication
Affected:>= 20.006.20034, <= 21.005.20060
Acrobat 2017Application
Affected:>= 17.011.30158, <= 17.011.30199
Acrobat Reader 2017Application
Affected:>= 17.011.30158, <= 17.011.30199
AcrobatApplication
Affected:>= 20.001.30005, <= 20.004.30006
Acrobat ReaderApplication
Affected:>= 20.001.30005, <= 20.004.30006

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
None
Availability
None

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

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. Locate installed Adobe Acrobat or Reader application
    On Windows, open Programs and Features or check the installation directory (typically C:\Program Files\Adobe\). On macOS, check the Applications folder for Adobe Acrobat or Adobe Acrobat Reader.
    Affected if Adobe Acrobat or Adobe Acrobat Reader is installed on the system
  2. Determine the installed version number
    On Windows, right-click the application executable (e.g., AcroRd32.exe for Reader or AcroDist.exe for Acrobat) and select Properties, then view the Details tab for the Product Version. On macOS, right-click the application, select Get Info, and view the Version field.
    Affected if The version number cannot be determined or is not visible
  3. Compare installed version against affected ranges
    Compare your installed version to the following affected ranges: 21.005.20060 and earlier for 2021.x versions; 20.004.30006 and earlier for 2020.x versions; 17.011.30199 and earlier for 2017.x versions; and any 20.x version from 20.001.30005 through 20.004.30006.
    Affected if The installed version falls within any of these ranges: 21.005.20060 or earlier; 20.004.30006 or earlier; 17.011.30199 or earlier; or between 20.001.30005 and 20.004.30006 inclusive
  4. Confirm the vulnerability trigger condition
    Note that successful exploitation requires a user to open a maliciously crafted PDF file. Check whether users in your environment commonly open PDF files from external or untrusted sources.
    Affected if Users routinely open PDF files from untrusted or unknown sources

A user is affected if Adobe Acrobat or Reader is installed with a version number matching any of the specified affected ranges, and a user could be convinced to open a malicious PDF file.

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 patched version provided by Adobe. Until patched, avoid opening PDF files from untrusted sources.

Recommended fix High confidence

Acrobat DC 2021.006.20001 or later; Acrobat DC 2020.004.30007 or later; Acrobat 2017.011.30200 or later

  1. 1. Open Adobe Acrobat or Adobe Reader on the affected system.
  2. 2. Navigate to Help > Check for Updates (or use the Help menu depending on your product version).
  3. 3. Allow Adobe to check for and download the latest available updates.
  4. 4. Follow the on-screen prompts to install the updates.
  5. 5. Alternatively, download the latest version directly from the official Adobe website at https://get.adobe.com/reader/ (for Reader) or https://get.adobe.com/acrobat/ (for Acrobat).
  6. 6. Verify the installed version matches or exceeds the fixed release by checking Help > About Adobe Acrobat Reader (or About Adobe Acrobat).
  7. 7. Ensure all instances of the application are closed before installing updates.
Caveat Standard Adobe update carries minimal risk; ensure backup of critical PDF files before updating

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

Fix this in Acrobat Dc Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,090
Get the upgrade done

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

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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-2021-39861 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