CVE-2021-35290
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 · uneditedFile Upload vulnerability in balerocms-src 0.8.3 allows remote attackers to run arbitrary code via rich text editor on /admin/main/mod-blog page.
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 confidenceA file upload vulnerability in balerocms-src 0.8.3 allows remote attackers to execute arbitrary code through the rich text editor on the /admin/main/mod-blog page. The rich text editor's file upload mechanism does not properly validate uploaded file types, allowing malicious files (such as PHP scripts) to be uploaded and executed 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= 0.8.3CVSS 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
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:H/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 Balero Cms versionCheck the version number in your installation - typically found in composer.json, a VERSION file, or the admin dashboard About section. Compare against the affected version 0.8.3.Affected if The installed version is exactly 0.8.3.
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Verify the admin blog module endpoint existsAttempt to access or check for the existence of the /admin/main/mod-blog route in your web server configuration or application routing. This is the page containing the vulnerable rich text editor.Affected if The /admin/main/mod-blog endpoint is accessible and the application responds.
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Confirm the rich text editor is enabledLog in to the admin panel and navigate to the blog module (or inspect the page source at /admin/main/mod-blog) to verify the rich text editor component is loaded and functional.Affected if The rich text editor is present and operational on the blog management page.
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Check file upload functionality in the editorWithin the rich text editor toolbar, look for and verify the presence of an image or file upload button/feature that accepts file attachments.Affected if The editor contains a file or image upload mechanism that can be invoked.
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Inspect upload directory configurationCheck your web server and application configuration to determine where uploaded files are stored and whether they are served from within the webroot.Affected if Uploaded files are stored in a location accessible via the web server (within webroot) and retain their original filename extensions.
You are affected if you are running Balero Cms version 0.8.3 with the rich text editor enabled on the /admin/main/mod-blog page and the file upload feature is accessible to remote users.
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 dataImplement strict file upload validation including allowlist-based extension checking, MIME type verification, content inspection, and storage of uploads outside the webroot or with renamed filenames. Disable script execution in upload directories and consider using a separate uploads domain.
- Consultation4.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,040.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-35290 — 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-2021-35290 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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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