Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Concrete CMS versions below 9.5.1 (the concrete5/concrete5 Packagist package) have a flaw in the RSS Displayer block, which accepts a feed URL from any page editor and fetches it on the server without validation. An attacker with page editor access could use this to make the server fetch internal resources via redirects. The source is brief and does not describe the exact impact. Upgrade to version 9.5.1, which is listed as the fixed release.
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
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 2.1 | Low | 4.0 | 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 | CNA (ConcreteCMS) |
- CISA KEV Not listed.
- EPSS 0.0015, the 4th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 13:58 UTC First seen by agentprime
- 31 Oct 2026, 13:58 UTC Confirmed by OSV