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CVE-2021-37770: Nucleus CMS v3.71 is affected by a file upload vulnerability.

Nucleus CMS v3.71 is affected by a file upload vulnerability. In this vulnerability, we can use upload to change the upload path to the path without the Htaccess file. Upload an Htaccess file and write it to AddType application / x-httpd-php.jpg. In this way, an attacker can upload a picture with shell, treat it as PHP, execute commands, so as to take down website resources.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-37770 describes a Nucleus CMS v3.71 file upload weakness that may let an attacker make uploaded image files execute as PHP. If reachable, this could lead to website compromise. The public record does not provide CVSS, a confirmed patch, or evidence of active exploitation.

Executive priority

Prioritize inventory and containment for any public Nucleus CMS v3.71 deployment. The likely impact is serious website compromise, but confidence is limited because public scoring, patch status, and exploitation evidence are incomplete.

Technical view

The source describes manipulating the upload path to a location without expected access controls, adding web server handling rules, then causing an uploaded image to be interpreted as PHP. This implies potential remote code execution through unsafe upload handling and server configuration interaction in Nucleus CMS v3.71.

Likely exposure

Exposure is most likely on internet-facing Nucleus CMS v3.71 sites where file upload functionality is enabled or reachable. The CVE record does not enumerate vendors, CPEs, authentication requirements, or affected configurations beyond the Nucleus CMS v3.71 description.

Exploitation context

The public description includes a vulnerability technique, but the CVE is not listed as KEV and the provided sources do not show active exploitation. Treat the details as public enough to increase urgency, while avoiding assumptions about real-world exploitation prevalence.

Researcher notes

Key gaps are CVSS, CWE mapping, CPEs, authentication requirements, and patch confirmation. The strongest claim supported by the bundle is unsafe upload handling that can cause uploaded content to execute as PHP under certain server path conditions.

Mitigation direction

  • Check Nucleus CMS guidance and issue 96 for fixed versions or vendor workarounds.
  • Restrict upload and administrative access until remediation status is confirmed.
  • Prevent uploaded media directories from executing server-side code.
  • Review upload paths for unexpected web server configuration files.
  • Remove suspicious uploaded files after preserving evidence for investigation.

Validation and detection

  • Confirm whether any deployed site runs Nucleus CMS v3.71.
  • Identify public or authenticated upload paths on affected deployments.
  • Review upload directories for unexpected configuration or executable media files.
  • Check web server logs for unusual uploads or path changes.
  • Verify vendor guidance before marking remediation complete.
Prepared
Confidence
medium
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

description · low confidence lookup

File access behavior lookup

The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-37770 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.