CVE-2021-21039
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 · moderate confidenceAdobe Acrobat Reader DC contains a Use After Free vulnerability where memory is accessed after being freed, potentially allowing an attacker to control execution flow and achieve arbitrary code execution in the context of the current user. Exploitation requires the victim to open a specially crafted 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.
-
Confirm Adobe Acrobat or Reader installationOn Windows, open Control Panel > Programs and Features, or check C:\Program Files\Adobe\ for Acrobat/Reader folders. On Mac, check /Applications for Adobe Acrobat or Adobe Reader.Affected if Adobe Acrobat or Adobe Acrobat Reader DC is installed on the system
-
Identify installed version on WindowsOpen Adobe Acrobat/Reader, then go to Help > About Adobe Acrobat Reader. Alternatively, run: reg query "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{AC76BA86-7AD7-1033-7B44-AC0F074E4100}" /v DisplayVersion (for Reader) or similar registry path for Acrobat.Affected if Version displayed matches any of the affected ranges
-
Identify installed version on MacOpen Adobe Acrobat/Reader from Applications, then go to Adobe Acrobat Reader DC > About Adobe Acrobat Reader (or Help > About on older versions).Affected if Version displayed matches any of the affected ranges
-
Compare against affected version rangesIf version starts with 17.x, ensure it is greater than 17.011.30188. If version starts with 20.x, ensure it is greater than 20.001.30018 (or 20.001.300183 for Reader) and greater than 20.013.20074 for DC variants.Affected if Installed version falls within 17.0 to 17.011.30188, 20.0 to 20.001.30018, or through 20.013.20074 for DC products
If Adobe Acrobat or Reader DC version is within the affected ranges and the user opens untrusted PDF files, the environment is vulnerable to CVE-2021-21039 exploitation.
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 the latest patched version beyond 2020.013.20074, 2020.001.30018, or 2017.011.30188 respectively. Additionally, enforce user awareness to avoid opening untrusted PDF files.
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,424.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21039 — 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-2021-21039 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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