Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
GeoServer versions below 2.26.4 and from 2.27.0 up to (but not including) 2.27.3, including the gs-web-app and gs-main Maven packages, are vulnerable to unauthenticated Server-Side Request Forgery through XML entity resolution when the ENTITY_RESOLUTION_ALLOWLIST is in use and a proxy base URL is configured. An attacker can cause GeoServer to make requests to unintended locations. Upgrade to 2.26.4, 2.27.3, or later. As a workaround, if the proxy base URL has no path, add a trailing slash to it.
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 |
|---|---|---|---|---|
| 6.5 | Medium | 3.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:L | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0029, the 21st percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:20 UTC First seen by agentprime
- 31 Oct 2026, 14:20 UTC Confirmed by OSV