Cyber Resilience

CVE-2026-28133

High

Published: 05 March 2026

Published
05 March 2026
Modified
22 April 2026
KEV Added
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Patch
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CVSS Score v3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
EPSS Score 0.0021 11.4th percentile
Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-28133 is a high-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability. Its CVSS base score is 8.1 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 11.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Deeper analysis

CVE-2026-28133 is an Unrestricted Upload of File with Dangerous Type vulnerability (CWE-434) in the WP Chill Filr filr-protection WordPress plugin. This issue affects Filr versions from n/a through 1.2.14 and carries a CVSS v3.1 base score of 8.1 (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N). The vulnerability enables attackers to upload web shells to the web server.

An authenticated attacker with low privileges can exploit this flaw over the network with low attack complexity and no user interaction required. Exploitation allows uploading dangerous files such as web shells, resulting in high impacts to confidentiality and integrity, potentially compromising the server.

The Patchstack advisory provides further details on mitigation for this arbitrary file upload vulnerability in the Filr Protection plugin: https://patchstack.com/database/Wordpress/Plugin/filr-protection/vulnerability/wordpress-filr-plugin-1-2-12-arbitrary-file-upload-vulnerability?_s_id=cve.

OWASP Top 10 for Web (2025)

A06:2025 Insecure Design

EU & UK References

Vulnerability details

Unrestricted Upload of File with Dangerous Type vulnerability in WP Chill Filr filr-protection allows Upload a Web Shell to a Web Server.This issue affects Filr: from n/a through <= 1.2.14.

CWE(s)
CWE-434

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1505.003 Web Shell Persistence
Adversaries may backdoor web servers with web shells to establish persistent access to systems.
attack.mitre.org →
Why these techniques?

Arbitrary file upload in public-facing WordPress plugin directly enables exploitation of public-facing apps (T1190) to deploy web shells (T1505.003).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2025-22654Shared CWE-434
CVE-2025-11948Shared CWE-434
CVE-2025-67260Shared CWE-434
CVE-2025-28915Shared CWE-434
CVE-2023-53956Shared CWE-434
CVE-2025-6058Shared CWE-434
CVE-2021-47819Shared CWE-434
CVE-2025-7852Shared CWE-434
CVE-2026-4883Shared CWE-434
CVE-2019-25630Shared CWE-434

Affected Assets

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-2 Flaw Remediation good match
prevent

Directly remediates the unrestricted file upload vulnerability in the Filr plugin by requiring timely identification, reporting, and patching of the flaw.

SI-10 Information Input Validation good match
prevent

Prevents exploitation of the CVE by enforcing validation of file inputs at upload endpoints to reject dangerous types like web shells.

SI-3 Malicious Code Protection good match
preventdetect

Mitigates uploaded web shells by scanning and blocking malicious code attempted via the unrestricted upload vulnerability.

References