CVE-2021-24857Public exploitNetwork attack vector

Unauthenticated object injection via unsafe unserialize

Published Dec 13, 2021 · Updated Aug 3, 2024

PHP object injection in Nocean ToTop Link 1.7.1 and earlier allows remote attackers to submit serialized objects via the vars parameter. The public totop-link.css.php endpoint base64-decodes attacker-controlled vars data and passes it to PHP unserialize() without validating the serialized object. No authentication or user interaction is required, but code execution or other application impact requires another installed plugin to provide a suitable PHP gadget chain.

CVSS severity9.8
Critical
EPSS probability1.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

PHP object injection in Nocean ToTop Link 1.7.1 and earlier allows remote attackers to submit serialized objects via the vars parameter. The public totop-link.css.php endpoint base64-decodes attacker-controlled vars data and passes it to PHP unserialize() without validating the serialized object. No authentication or user interaction is required, but code execution or other application impact requires another installed plugin to provide a suitable PHP gadget chain.

The record

CVE
CVE-2021-24857
Published
Dec 13, 2021
Updated
Aug 3, 2024
Vendor
Nocean
Product
ToTop Link
Classifications
CWE-502, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 13, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.7.1 <=1.7.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nocean · ToTop Linkversion=1.7.1 <=1.7.1

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.

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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-502Deserialization of Untrusted Data
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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