CVE-2020-21787Public exploitNetwork attack vector

Remote code execution via Windows upload suffix bypass

Published Jun 24, 2021 · Updated Aug 4, 2024

Unrestricted file upload in CRMEB 3.1.0+ allows remote attackers to execute PHP code through a crafted upload on Windows servers. UploadService.php's file() method trusts getOriginalExtension() and checks only the apparent suffix, without rejecting the Windows ::$DATA stream suffix. Windows removes ::$DATA from the stored name, leaving an executable .php file; an enabled file-upload setting must expose the upload path.

CVSS severity9.8
Critical
EPSS probability1.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unrestricted file upload in CRMEB 3.1.0+ allows remote attackers to execute PHP code through a crafted upload on Windows servers. UploadService.php's file() method trusts getOriginalExtension() and checks only the apparent suffix, without rejecting the Windows ::$DATA stream suffix. Windows removes ::$DATA from the stored name, leaving an executable .php file; an enabled file-upload setting must expose the upload path.

The record

CVE
CVE-2020-21787
Published
Jun 24, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-434, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10.0NIST NVDAV:N/AC:L/Au:N/C:C/I:C/A:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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