CVE-2021-27309Public exploitNetwork attack vector

Unauthenticated reflected XSS via module parameter

Published Mar 23, 2021 · Updated Aug 3, 2024

Reflected cross-site scripting in Clansphere CMS 2011.4 allows remote attackers to execute script in a victim's browser via the module parameter. The vulnerable endpoint reflects the module query value into generated HTML without neutralizing script characters, enabling crafted payloads to run in the page context. Exploitation requires a victim to follow or load a malicious link; executed script can steal session data, alter displayed content, or redirect the victim, while the record reports no direct server compromise.

CVSS severity6.1
Medium
EPSS probability1.97%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected cross-site scripting in Clansphere CMS 2011.4 allows remote attackers to execute script in a victim's browser via the module parameter. The vulnerable endpoint reflects the module query value into generated HTML without neutralizing script characters, enabling crafted payloads to run in the page context. Exploitation requires a victim to follow or load a malicious link; executed script can steal session data, alter displayed content, or redirect the victim, while the record reports no direct server compromise.

The record

CVE
CVE-2021-27309
Published
Mar 23, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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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