Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Craft CMS versions 4.0.0-RC1 up to 4.17.9 and 5.0.0-RC1 up to 5.9.15 are affected through the resource-js endpoint, which proxies remote JavaScript resources and can be reached without authentication when trustedHosts is not restricted. An unauthenticated attacker can send a forged Host header so the server accepts an arbitrary URL and makes requests to hosts of their choosing, which is a server-side request forgery. Upgrade to Craft CMS 4.17.9 or 5.9.15, or later. As a workaround, set trustedHosts to the hostnames your site should serve.
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 |
|---|---|---|---|---|
| 5.5 | Medium | 4.0 | CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0033, the 26th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:25 UTC First seen by agentprime
- 31 Oct 2026, 14:25 UTC Confirmed by OSV