CVE-2023-53933Public exploitNetwork attack vectorHinoki check available

Authenticated command execution via unrestricted .phar upload

Published Dec 17, 2025 · Updated Dec 17, 2025

Unrestricted file upload in Serendipity 2.4.0 allows remote authenticated users to execute arbitrary server commands via a .phar file. The media-library upload action accepts a PHP-bearing .phar category image and stores it under the web-accessible uploads path without blocking the dangerous type. A valid backend session and CSRF token are required; requesting the stored file executes its PHP payload with the web server's privileges.

CVSS severity8.7
High
EPSS probability1.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Unrestricted file upload in Serendipity 2.4.0 allows remote authenticated users to execute arbitrary server commands via a .phar file. The media-library upload action accepts a PHP-bearing .phar category image and stores it under the web-accessible uploads path without blocking the dangerous type. A valid backend session and CSRF token are required; requesting the stored file executes its PHP payload with the web server's privileges.

The record

CVE
CVE-2023-53933
Published
Dec 17, 2025
Updated
Dec 17, 2025
Vendor
Serendipity Team
Product
Serendipity
Classifications
CWE-434, T1505.003
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 17, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 17, 2025Record 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=2.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Serendipity Team · Serendipityversion=2.4.0

Published CVSS scores

8.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA: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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
T1505.003Server Software Component: Web 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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