CVE-2020-21865Network attack vector

Unauthenticated remote code execution

Published Oct 7, 2021 · Updated Aug 4, 2024

Remote code execution in ThinkPHP50-CMS 1.0 allows remote attackers to execute arbitrary code through the /public/?s=captcha endpoint. The CNA-linked report attributes the flaw to bundled ThinkPHP 5.0.18 but does not disclose the exact code path or operation performed on untrusted input. No authentication or user interaction is required, and successful exploitation grants control over the web application and its accessible data.

CVSS severity9.8
Critical
EPSS probability2.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in ThinkPHP50-CMS 1.0 allows remote attackers to execute arbitrary code through the /public/?s=captcha endpoint. The CNA-linked report attributes the flaw to bundled ThinkPHP 5.0.18 but does not disclose the exact code path or operation performed on untrusted input. No authentication or user interaction is required, and successful exploitation grants control over the web application and its accessible data.

The record

CVE
CVE-2020-21865
Published
Oct 7, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 7, 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

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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 exploitUnconfirmed

Weakness, pattern, technique

T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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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