CVE-2021-34840
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 · uneditedThis vulnerability allows remote attackers to execute arbitrary code on affected installations of Foxit PDF Reader 11.0.0.49893. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the handling of Annotation objects. The issue results from the lack of validating the existence of an object prior to performing operations on the object. An attacker can leverage this vulnerability to execute code in the context of the current process. Was ZDI-CAN-14021.
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 Foxit PDF Reader's Annotation object handling where the software fails to validate object existence prior to performing operations on it. Attackers can exploit this by crafting malicious PDF files that trigger the vulnerability, allowing arbitrary code execution in the context of the current user process.
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<= 11.0.0.49893<= 10.1.4.37651= 11.0.0.49893CVSS 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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Identify installed Foxit productOpen Windows Control Panel > Programs and Features, or macOS Applications folder. Look for 'Foxit PDF Reader' or 'Foxit PDF Editor' in the installed programs list.Affected if Neither Foxit PDF Reader nor Foxit PDF Editor is installed - the vulnerability does not apply.
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Check installed Foxit versionIn Foxit PDF Reader/Editor, go to Help > About Foxit PDF Reader/Editor. The version number displayed must be compared to affected ranges.Affected if Version is 11.0.0.49893 or lower for Reader; or 10.1.4.37651 or lower, or exactly 11.0.0.49893 for Editor - the version is vulnerable.
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Confirm JavaScript execution is availableIn Foxit Reader/Editor, go to Edit > Preferences > JavaScript. Check if JavaScript is enabled.Affected if JavaScript is enabled - the attack surface for exploiting this use-after-free via malicious PDF is present.
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Verify PDF file handling capabilityAttempt to open any PDF file in the Foxit application to confirm the PDF processing component is functional.Affected if PDF files open successfully - the application can process PDF documents and the vulnerable Annotation handling code path is reachable.
You are affected if Foxit PDF Reader version 11.0.0.49893 or lower, or Foxit PDF Editor version 10.1.4.37651 or lower or exactly 11.0.0.49893, is installed and the application can process PDF files.
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 Foxit PDF Reader to the latest patched version. Users should avoid opening PDF files from untrusted sources and disable JavaScript execution in the reader as an additional hardening measure.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2021-34840 — 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-2021-34840 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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