CVE-2021-21040
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 versions 2020.013.20074 (and earlier), 2020.001.30018 (and earlier) and 2017.011.30188 (and earlier) are affected by a Use After Free vulnerability. An unauthenticated attacker could leverage this vulnerability to achieve 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 · high confidenceUse After Free vulnerability in Adobe Acrobat Reader DC allowing arbitrary code execution in the current user's context. Exploitation requires victim to open a 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>= 17.0, <= 17.011.30188>= 20.0, <= 20.001.30018<= 20.013.20074>= 17.0, <= 17.011.30188>= 20.0, <= 20.001.300183<= 20.013.20074CVSS 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:3.1/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.
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Check if Adobe Acrobat Reader DC is installedOn Windows, open Control Panel > Programs and Features, or check the registry at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\AcroRd32.exe. On macOS, check /Applications for Adobe Acrobat Reader DC.appAffected if Adobe Acrobat Reader DC or Adobe Acrobat is present on the system
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Determine the installed version numberRight-click the Adobe Acrobat Reader icon, select Properties, and view the Details tab for the Version field. Or, open the application, go to Help > About Adobe Acrobat Reader to see the exact version build numberAffected if The version number is visible and can be compared against affected ranges
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Compare installed version against affected rangesMatch your version against these vulnerable ranges: Adobe Acrobat/Reader 17.x up to 17.011.30188; Adobe Acrobat/Reader 20.x up to 20.001.30018/300183; Adobe Acrobat/Reader DC up to 20.013.20074Affected if Your installed version falls within any of these ranges: 17.0 through 17.011.30188, 20.0 through 20.001.30018 (or 300183), or any DC variant through 20.013.20074
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Determine if the application handles PDF filesCheck if Adobe Acrobat Reader is set as the default PDF handler, or if you frequently open PDF files using this application. This is the exploitation vectorAffected if Adobe Acrobat Reader DC is used to open PDF files from untrusted sources
You are affected if Adobe Acrobat Reader DC or Adobe Acrobat is installed with a version matching the ranges 17.0-17.011.30188, 20.0-20.001.30018, or DC variants through 20.013.20074, and you open PDF files with it.
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.
From vendor dataUpdate Adobe Acrobat Reader DC to patched versions (2020.013.20075, 2020.001.30019, or 2017.011.30189 and later). Avoid opening untrusted PDF files until patched.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21040 — 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-2021-21040 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
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- 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