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GetsimplecmsApplication · Get Simple

CVE-2021-28976

HIGH · 7.2 CVSS v3.1 Published 2021-06-23
Fix available
A fix is available. Upgrade to 3.3.15 or later.
See remediation →
78/100
Remediation priority · High
Remotely reachable Zero-click

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 · unedited
Remote Code Execution vulnerability in GetSimpleCMS before 3.3.16 in admin/upload.php via phar filess.

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 confidence

GetSimpleCMS before version 3.3.16 contains a Remote Code Execution vulnerability in admin/upload.php. The vulnerability allows attackers to upload malicious PHP Archive (phar) files which, when deserialized by the application, can execute arbitrary PHP code on the server.

MitigationUpgrade GetSimpleCMS to version 3.3.16 or later. Until patched, disable file upload functionality in admin/upload.php or restrict access to the admin area to trusted users only.

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
GetsimplecmsApplication
Affected:< 3.3.15

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify GetSimpleCMS installation
    Locate GetSimpleCMS in your web root directory (typically look for gsconfig.php, index.php, or the /admin/ folder)
    Affected if GetSimpleCMS files are present in your web directory
  2. Check installed version
    Open the admin dashboard or look for a version identifier in includes/gsversion.php, changelog, or admin about page - compare this version number to 3.3.15
    Affected if The installed version is less than 3.3.15 (for example, 3.3.14, 3.3.13, etc.)
  3. Verify admin/upload.php exists
    Check for the file admin/upload.php in your GetSimpleCMS installation directory
    Affected if The file admin/upload.php exists and is accessible via the web
  4. Confirm admin area accessibility
    Attempt to access the /admin/ login page or verify the admin directory is not protected by additional authentication beyond GetSimpleCMS credentials
    Affected if The admin area is exposed and reachable over the network

You are affected if GetSimpleCMS version is below 3.3.16 AND the admin/upload.php file exists and is accessible on your server.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to 3.3.15 or later
Fixed in 3.3.15
Interim mitigation

Upgrade GetSimpleCMS to version 3.3.16 or later. Until patched, disable file upload functionality in admin/upload.php or restrict access to the admin area to trusted users only.

Fix this in Getsimplecms Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

Scan for this in your stack

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dbcve dependency scanner

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-28976 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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