CVE-2023-53933
S9Y Serendipity 2.4.0
Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2023-53933 is a high-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability in S9Y Serendipity. Its CVSS base score is 8.7 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 43% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SI-3 (Malicious Code Protection) and CM-7 (Least Functionality) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2023-53933 is a remote code execution vulnerability in Serendipity 2.4.0, a PHP-based blogging platform. The flaw allows authenticated attackers to upload malicious PHP files with a .phar extension via the media upload endpoint. These files can contain system command payloads, enabling arbitrary command execution on the affected server. The vulnerability is rated with a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and is associated with CWE-434 (Unrestricted Upload of File with Dangerous Type).
An attacker with low-privilege authenticated access, such as a registered user, can exploit this vulnerability remotely over the network with low complexity and no user interaction required. By crafting and uploading a .phar file containing malicious payloads to the media endpoint, the attacker achieves full remote code execution on the server, potentially leading to high confidentiality, integrity, and availability impacts, including server compromise, data theft, or further lateral movement.
Advisories and related resources, including the Serendipity documentation at https://docs.s9y.org/, a VulnCheck advisory at https://www.vulncheck.com/advisories/serendipity-authenticated-remote-code-execution-via-file-upload, and a public proof-of-concept exploit at https://www.exploit-db.com/exploits/51372, provide further details on the issue. Security practitioners should consult these for recommended mitigations, such as restricting upload permissions or applying any available patches.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-60198
Vulnerability Data
Serendipity 2.4.0 contains a remote code execution vulnerability that allows authenticated attackers to upload malicious PHP files with .phar extension. Attackers can upload files with system command payloads to the media upload endpoint and execute arbitrary commands on the server.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V5.1.1
Mitigating Controls (NIST 800-53 r5) AI
Malicious-code protection at entry points blocks dangerous file types from being accepted and executed.
Least functionality restricts the file types and automatic processing capabilities the system will accept.
Mobile-code controls define, authorize, and block unacceptable uploaded code before automatic processing occurs.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Restricting execution of unauthorized software directly blocks dangerous uploaded files from running.
Hardened configuration baselines can enforce allowed file types and processing rules.
Secure development practices include input validation and file-type restrictions that prevent this weakness.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Configuration and acceptance testing verify that file-upload handling enforces allowed types and does not permit dangerous content to be stored or executed.
Secure-coding guidelines and security testing explicitly address restrictions on allowed file types and upload handling, reducing the risk that dangerous file uploads are accepted without validation.
Mandated testing for malicious content and known vulnerabilities reduces the likelihood that an outsourced component will contain or accept dangerous file types that could later be uploaded or executed.
Application allow-listing and pre-use scanning of received files directly blocks the introduction of executable content that has not been vetted, eliminating the primary vector for unrestricted dangerous file uploads.