CVE-2021-27581
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 · uneditedThe Blog module in Kentico CMS 5.5 R2 build 5.5.3996 allows SQL injection via the tagname parameter.
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 confidenceSQL injection vulnerability in the Blog module of Kentico CMS 5.5 R2 (build 5.5.3996) allows unauthenticated attackers to inject malicious SQL queries through the tagname parameter, potentially enabling data exfiltration, authentication bypass, or complete database compromise.
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= 5.5CVSS 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 installed Kentico CMS versionAccess the Kentico administration interface and navigate to the 'About' section, or check the CMSWebApp assembly version in the bin directory. Alternatively, locate the version.txt or release notes file in the installation directory.Affected if The version displayed is Kentico CMS 5.5 (build 5.5.3996) exactly.
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Determine if Blog module is installedLog into the Kentico CMS administration dashboard and check the 'Modules' section to see if the 'Blog' module is listed as installed and enabled.Affected if The Blog module is present and enabled in the Kentico CMS installation.
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Locate Blog module functionality using tagname parameterInspect the Blog module handlers or URL routing configuration, typically found under /CMSModules/Blogs/ or similar paths. Look for aspx pages that accept a 'tagname' query string parameter in the Blog-related URLs.Affected if URLs or pages exist that accept a tagname parameter within the Blog module functionality.
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Verify unauthenticated access to Blog tagname endpointAttempt to access a Blog page with a tagname parameter (e.g., /CMSPages/Blog.aspx?tagname=test) without providing any authentication credentials.Affected if The request returns a valid page response without requiring login, indicating the endpoint is accessible to unauthenticated users.
A system is affected if it runs Kentico CMS version 5.5 with the Blog module installed and exposes a tagname parameter endpoint that can be accessed without authentication.
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 dataUpgrade to a patched version of Kentico CMS or apply the vendor-supplied security patch that implements parameterized queries for the tagname parameter in the Blog module.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27581 — 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-2021-27581 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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