RSS Displayer Block Server-Side Request Forgery in Concrete CMS

Publication date: 2026-05-21

Last updated on: 2026-05-22

Assigner: ConcreteCMS

Description

In Concrete CMS 9.5.0 and below, the RSS Displayer block accepts a feed URL from any page editor and fetches it server-side without validation enabling redirect-to-internal bypasses. The Concrete CMS security team gave this vulnerability a CVSS v.4.0 score of 2.1 with a vector CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:L/VA:N/SC:L/SI:N/SA:N.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-05-21

Last Modified

2026-05-22

Generated

2026-07-02

AI Q&A

2026-05-22

EPSS Evaluated

2026-06-30

NVD

CVE-2026-7890

EUVD

EUVD-2026-31379

Affected Vendors & Products

Vendor	Product	Version / Range
concretecms	concrete_cms	to 9.5.1 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-918	The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

Attack-Flow Graph

Executive Summary

This vulnerability exists in Concrete CMS version 9.5.0 and below, specifically in the RSS Displayer block. The block accepts a feed URL from any page editor and fetches it server-side without validating the URL properly. This lack of validation allows attackers to perform redirect-to-internal bypasses.

Impact Analysis

The vulnerability could allow an attacker with high privileges (page editor) to cause the server to fetch unintended internal resources by bypassing URL validation. This could potentially lead to information disclosure or other unintended server-side actions, although the overall severity is low as indicated by the CVSS score of 2.1.

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