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AcrobatApplication · Adobe

CVE-2021-39850

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 · high confidence

A null pointer dereference vulnerability in Adobe Acrobat Reader DC allows an unauthenticated attacker to cause an application denial-of-service by tricking a victim into opening a maliciously crafted PDF file. The attack crashes the application but does not appear to achieve code execution.

MitigationApply the vendor-supplied Adobe security updates to all affected Acrobat Reader DC versions (2021.005.20060 and earlier, 2020.004.30006 and earlier, 2017.011.30199 and earlier). Users should avoid opening untrusted PDF files as a defense-in-depth measure.

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 Reader or Acrobat, then go to Help > About Adobe Acrobat Reader (or Acrobat). Alternatively, right-click the application shortcut and select Properties, then look at the File version on the Details tab.
    Affected if The installed product is Adobe Acrobat, Adobe Acrobat Reader, Adobe Acrobat DC, or Adobe Acrobat Reader DC.
  2. Determine the exact version number
    Note the full version number displayed in the About dialog (for example: 20.004.30006 or 21.005.20058). Record all three version segments.
    Affected if A version number is displayed that can be compared against the affected ranges.
  3. Check if the version falls within the affected ranges
    Compare your installed version against these affected ranges: Acrobat/Acrobat Reader 20.x (20.001.30005 through 20.004.30006), 17.x (17.011.30059 through 17.011.30199); Acrobat DC/Reader DC 15.x through 21.x (15.008.20082 through 21.005.20058 or 21.005.20060 depending on the track).
    Affected if The installed version is greater than or equal to the lower bound AND less than or equal to the upper bound of any affected range listed.
  4. Confirm the product variant and track
    Determine if you have standard Acrobat/Reader or the DC (Document Cloud) variant, as the DC versions have a separate affected range (15.008.20082 through 21.005.20058/20060). Check the product name in the About dialog or installed program name.
    Affected if The product is Adobe Acrobat DC or Adobe Acrobat Reader DC with versions 15.008.20082 through 21.005.20058 or 21.005.20060.

A user is affected if they have any Adobe Acrobat, Acrobat Reader, Acrobat DC, or Reader DC version within the specified ranges and open a maliciously crafted PDF file, which would cause the application to crash.

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

Apply the vendor-supplied Adobe security updates to all affected Acrobat Reader DC versions (2021.005.20060 and earlier, 2020.004.30006 and earlier, 2017.011.30199 and earlier). Users should avoid opening untrusted PDF files as a defense-in-depth measure.

Recommended fix High confidence

Adobe Acrobat/Reader DC 2021.006.20060+ (Continuous) or 2021.005.20061+ (Classic); Acrobat/Reader 2020.004.30007+; Acrobat/Reader 2017.011.30200+

  1. 1. Determine your installed Adobe Acrobat/Reader version by opening the application, then going to Help > About Adobe Acrobat (or Reader)
  2. 2. Identify which track (Continuous or Classic) and version year (2017, 2020, or 2021) your installation matches
  3. 3. For Adobe Acrobat/Reader DC (Continuous track): Upgrade to version 2021.006.20060 or later
  4. 4. For Adobe Acrobat/Reader DC (Classic track): Upgrade to version 2021.005.20061 or later
  5. 5. For Adobe Acrobat/Reader 2020: Upgrade to version 2020.004.30007 or later
  6. 6. For Adobe Acrobat/Reader 2017: Upgrade to version 2017.011.30200 or later
  7. 7. Download the appropriate updated version from the official Adobe website (get.adobe.com/reader for Reader or adobe.com for Acrobat)
  8. 8. Close all Adobe applications and run the installer to apply the update
Caveat Standard Adobe update—minor version bump with security fixes; no major functionality changes expected

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

Fix this in Acrobat 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-2021-39850 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