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Advisory record · GHSA-5rj5-gfmr-hrc3

Concrete CMS does not validate a CSRF token before processing requests to `/dashboard/extend/update/prepare_remote_upgrade/<remoteMPID>`

CVSS 7.5 HighEPSS 0.0017 · 6th percentile

Published by the GitHub Advisory Database at 21 May 2026, 21:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
concrete5/concrete5Packagist<9.5.19.5.1
Identifiers
GHSA-5rj5-gfmr-hrc3 · CVE-2026-8426 · PKSA-61mc-443r-dbcf
Weakness (CWE)
CWE-352 · CWE-829
Tags
Published
21 May 2026
Updated
10 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Concrete CMS packages affected by this advisory are concrete5/concrete5 versions before 9.5.1, with 9.5.1 as the fixed release. The endpoint for remote upgrades does not check a CSRF token, so an attacker who controls the remote package served for a marketplace item already installed on the site can get a logged-in administrator with package-install rights to visit a crafted page and trigger remote code execution as the web server user. The victim must be able to install packages and the site must be connected to the Concrete marketplace. Upgrade to Concrete CMS 9.5.1 or later.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.5 High 4.0 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N CNA (ConcreteCMS)
  • CISA KEV Not listed.
  • EPSS 0.0017, the 6th percentile, on 6 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 13:59 UTC First seen by agentprime
  2. 31 Oct 2026, 13:59 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.