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Low, CVSS 2.1

Concrete CMS's RSS Displayer block accepts a feed URL from any page editor and fetches it server-side without validation

CVE-2026-7890GHSA-gjwq-9v8p-47w7

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (concrete5/concrete5 9.5.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
2.1 · 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 · score source
EPSS
  • CVE-2026-7890: 0.15% estimated exploitation activity in the next 30 days; percentile 4.41 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-gjwq-9v8p-47w7

Agent brief

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# Patch Next advisory brief: CVE-2026-7890

Advisory: Concrete CMS's RSS Displayer block accepts a feed URL from any page editor and fetches it server-side without validation
IDs: CVE-2026-7890, GHSA-gjwq-9v8p-47w7
Record: https://patchnext.com/advisories/cve-2026-7890 (revision 1, source checked 26 Oct 2026, 14:49 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: concrete5/concrete5 9.5.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist concrete5/concrete5: affected < 9.5.1; fixed in 9.5.1

## Suggested inspection (read-only)
- Packagist concrete5/concrete5: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on concrete5/concrete5.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-gjwq-9v8p-47w7 (GitHub-reviewed advisory GHSA-gjwq-9v8p-47w7 lists affected ranges: Packagist concrete5/concrete5 >=0 <9.5.1)

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