CVE-2021-21028
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 confidenceA Use After Free vulnerability exists in Adobe Acrobat Reader DC that allows an attacker to achieve arbitrary code execution by tricking a user into opening a malicious PDF file. The vulnerability exploits freed memory that is still referenced, potentially allowing the attacker to control memory contents and execute arbitrary code in the context of the current user.
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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/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 is installedOn Windows, open Control Panel > Programs and Features, or run 'Get-ItemProperty HKLM:\Software\Microsoft\Windows\CurrentVersion\Uninstall\* | Select-Object DisplayName, DisplayVersion' in PowerShell. On macOS, check /Applications for Adobe Acrobat Reader DC.appAffected if Adobe Acrobat Reader or Adobe Acrobat appears in the installed programs list
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Determine the exact installed versionOpen Adobe Acrobat Reader/Acrobat, then go to Help > About Adobe Acrobat Reader/Acrobat. Alternatively, right-click the application in Programs and Features and select Properties to view the version fieldAffected if The version displayed does not match the patched versions (2020.013.20075 or later for 2020 track, or corresponding patched versions for other tracks)
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Compare your version against affected rangesUse the version found in the previous step and check if it falls within: 17.0 to 17.011.30188, 20.0 to 20.001.30018 (Acrobat), 20.0 to 20.001.300183 (Reader), or any version 20.013.20074 or earlier for DC variantsAffected if Your installed version falls within any of the affected version ranges listed
You are affected if Adobe Acrobat Reader or Adobe Acrobat is installed and the version number falls within 17.0-17.011.30188, 20.0-20.001.30018/20.001.300183, or is 20.013.20074 or earlier for DC variants.
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 dataApply the vendor patch by updating to the latest version of Adobe Acrobat Reader DC (2020.013.20075 or later for the 2020 track, and corresponding patched versions for other tracks). Avoid opening untrusted or unexpected PDF files from unverified sources.
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21028 — 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-2021-21028 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
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