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AcrobatApplication · Adobe

CVE-2021-39849

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 a Null pointer dereference vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve an application denial-of-service 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 null pointer dereference vulnerability that can be triggered when a user opens a specially crafted malicious PDF file. An unauthenticated attacker can cause the application to crash, resulting in denial-of-service in the context of the current user.

MitigationUpdate Adobe Acrobat Reader DC to a version later than 2021.005.20060, 2020.004.30006, or 2017.011.30199 as applicable. Additionally, exercise caution when 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
AcrobatApplication
Affected:>= 20.001.30005, <= 20.004.30006>= 17.011.30059, <= 17.011.30199
Acrobat ReaderApplication
Affected:>= 20.001.30005, <= 20.004.30006>= 17.011.30059, <= 17.011.30199
Acrobat DcApplication
Affected:>= 15.008.20082, <= 21.005.20058>= 15.008.20082, <= 21.005.20060
Acrobat Reader DcApplication
Affected:>= 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
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/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 the installed Adobe product
    Open Adobe Acrobat or Reader, go to Help > About Adobe Acrobat Reader (or similar About option). Note whether it is Acrobat or Acrobat Reader, and whether it is the Classic or Continuous version.
    Affected if The product is Adobe Acrobat or Adobe Acrobat Reader (any variant) in the affected version ranges.
  2. Determine the exact version number
    In the About dialog, record the full version number (for example: 20.004.30006, 17.011.30199, 21.005.20058, or 15.008.20082).
    Affected if The version falls within any of the affected ranges: 20.001.30005 to 20.004.30006, 17.011.30059 to 17.011.30199, 15.008.20082 to 21.005.20058, or 15.008.20082 to 21.005.20060.
  3. Confirm the product variant and track
    Check if the installation is Classic (2020, 2017, 2015) or Continuous (2021, 2022) track. This is visible in the product name or About dialog.
    Affected if The version matches the affected ranges for either Classic or Continuous track as listed in the CVE.
  4. Verify PDF processing capability
    Confirm the application is configured to open PDF files. This is the default state for Acrobat Reader and Acrobat.
    Affected if The application can open PDF files, which is always enabled by default in these products.

A user is affected if they have Adobe Acrobat or Acrobat Reader DC installed with a version matching any of the listed vulnerable ranges.

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 a version later than 2021.005.20060, 2020.004.30006, or 2017.011.30199 as applicable. Additionally, exercise caution when opening PDF files from untrusted sources.

Recommended fix High confidence

Adobe Acrobat/Reader DC 2021.006.20030+ (Continuous); Acrobat/Reader 2020.004.30007+ (Classic); Acrobat/Reader 2017.011.30200+ (Classic)

  1. 1. Identify the currently installed Adobe Acrobat or Acrobat Reader version by opening the application and navigating to Help > About Adobe Acrobat (or Reader)
  2. 2. Determine which product line and version branch you are using (2017.x, 2020.x, or 2021.x)
  3. 3. For Adobe Acrobat/Reader DC (Continuous track): Upgrade to version 2021.006.20030 or later
  4. 4. For Adobe Acrobat/Reader 2020 (Classic track): Upgrade to version 2020.004.30007 or later
  5. 5. For Adobe Acrobat/Reader 2017 (Classic track): Upgrade to version 2017.011.30200 or later
  6. 6. Download the updated version from the official Adobe website or use your organization's software distribution tool
  7. 7. Close all Adobe applications before installing the update
  8. 8. Run the installer and follow the prompts to complete the upgrade
Caveat Standard Adobe update - minimal risk; ensure compatibility with any plugins or integration systems used in your environment

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

Fix this in Acrobat 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-2021-39849 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