CVE-2021-27220
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 PRTG Network Monitor before 21.1.66.1623. By invoking the screenshot functionality with prepared context paths, an attacker is able to verify the existence of certain files on the filesystem of the PRTG's Web 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 · moderate confidenceThe vulnerability allows unauthenticated attackers to verify file existence on the PRTG web server filesystem by manipulating context path parameters in the screenshot functionality. This information disclosure enables reconnaissance that could aid in planning further attacks, though it does not directly expose file contents.
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< 21.1.66.1623CVSS 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
- Low
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
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 PRTG Network Monitor versionAccess the PRTG web interface and navigate to Setup > About PRTG, or check the version displayed on the login page. Alternatively, check the installed software version on the server where PRTG is hosted.Affected if The installed version is lower than 21.1.66.1623
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Confirm screenshot functionality is accessiblePRTG Network Monitor includes a screenshot feature typically accessible to authenticated users. Verify if the web interface responds to requests for screenshot-related endpoints (e.g., /screenshot or similar paths in the PRTG web application).Affected if The screenshot functionality is enabled and accessible via the PRTG web interface
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Check for unauthenticated access to screenshot endpointsAttempt to access PRTG screenshot-related URLs without authentication. The vulnerability allows unauthenticated attackers to manipulate context path parameters to probe file existence.Affected if Unauthenticated requests to screenshot functionality return any response indicating file existence or path validation (even without content disclosure), confirming the vulnerability is exploitable.
If the installed PRTG Network Monitor version is below 21.1.66.1623 and the web interface is accessible, the environment is likely affected by this path traversal vulnerability that allows unauthenticated file existence verification.
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 data21.1.66.1623
Upgrade PRTG Network Monitor to version 21.1.66.1623 or later to apply the vendor patch addressing this path traversal issue.
- Consultation1.0 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-2021-27220 — 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-2021-27220 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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- Version or environment caveats, and links to real fixes
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