CVE-2020-11534
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 · uneditedAn issue was discovered in ONLYOFFICE Document Server 5.5.0. An attacker can craft a malicious .docx file, and exploit the NSFileDownloader function to pass parameters to a binary (such as curl or wget) and remotely execute code on a victim's server.
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 command injection vulnerability in ONLYOFFICE Document Server 5.5.0 allows attackers to embed malicious payloads in .docx files that are processed by the NSFileDownloader function. This function insecurely passes user-controlled parameters from the document to system binaries like curl or wget, enabling remote code execution on the server.
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= 5.5.0CVSS 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
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 the installed ONLYOFFICE Document Server versionRun the command: grep -r 'DocumentServer' /usr/local/etc/onlyoffice 2>/dev/null || cat /etc/onlyoffice/documentserver/default.json 2>/dev/null | grep -i version || dpkg -l | grep onlyoffice-documentserverAffected if The installed version is exactly 5.5.0 (only this version is vulnerable)
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Verify the NSFileDownloader component is presentSearch for the NSFileDownloader function in the codebase: find /var/www/onlyoffice -name '*.js' -o -name '*.ts' | xargs grep -l 'NSFileDownloader' 2>/dev/nullAffected if The NSFileDownloader function exists in the installation and handles document downloads
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Confirm document processing accepts .docx files from external sourcesReview the server configuration: cat /etc/onlyoffice/documentserver/default.json | grep -A10 'services'Affected if The server is configured to process .docx files uploaded by users or received from untrusted sources
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Examine server logs for suspicious download activityReview document server logs for curl/wget commands: grep -r 'curl\|wget' /var/log/onlyoffice/documentserver/ 2>/dev/null | head -50Affected if Logs show unexpected or malformed curl/wget calls with user-supplied parameters
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Check for unexpected outbound network connectionsMonitor or review network connections from the document server process: ss -tnp | grep -E 'curl|wget' or review firewall logs for unusual outbound connections from the serverAffected if The server is making outbound connections to unexpected or malicious addresses triggered by document processing
A user is affected if they are running ONLYOFFICE Document Server version 5.5.0 and the server processes .docx files from users or external sources via the NSFileDownloader function.
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 dataImmediately update to a patched version of ONLYOFFICE Document Server. If patching is not immediately possible, restrict network access to the document server and implement strict input validation on document processing functions as a temporary measure.
- Consultation3.0 h
- Implementation6.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2020-11534 — 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-2020-11534 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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