CVE-2021-36564Public exploitNetwork attack vector

Arbitrary file write via deserialization gadget chain

Published Dec 6, 2021 · Updated Aug 4, 2024

Deserialization in ThinkPHP 6.0.8 allows remote attackers to write arbitrary files through crafted serialized PHP objects. Adapter::__destruct invokes save on attacker-controlled adapter and file properties, reaching Local::write and file_put_contents with an attacker-chosen path and content. Exploitation requires an application endpoint that passes untrusted data to PHP unserialize; a writable web root turns the file write into PHP code execution.

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

Deserialization in ThinkPHP 6.0.8 allows remote attackers to write arbitrary files through crafted serialized PHP objects. Adapter::__destruct invokes save on attacker-controlled adapter and file properties, reaching Local::write and file_put_contents with an attacker-chosen path and content. Exploitation requires an application endpoint that passes untrusted data to PHP unserialize; a writable web root turns the file write into PHP code execution.

The record

CVE
CVE-2021-36564
Published
Dec 6, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-502, T1505.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 6, 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

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS: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
T1505.003Web Shell

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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