Description
A flaw was found in RESTEasy's CorsFilter, which, when configured to allow all origins ("*"), reflects the request's Origin header back in the Access-Control-Allow-Origin response together with Access-Control-Allow-Credentials: true. This permissive cross-origin policy allows a malicious website to make credentialed cross-origin requests and read authenticated responses from a victim's session, resulting in a loss of confidentiality.
References10
- access.redhat.com/errata/RHSA-2026:83082
- access.redhat.com/errata/RHSA-2026:83520
- access.redhat.com/errata/RHSA-2026:83670
- access.redhat.com/errata/RHSA-2026:85234
- access.redhat.com/errata/RHSA-2026:92408
- access.redhat.com/errata/RHSA-2026:95221
- access.redhat.com/errata/RHSA-2026:95466
- access.redhat.com/errata/RHSA-2026:95504
- access.redhat.com/errata/RHSA-2026:95505
- access.redhat.com/errata/RHSA-2026:95887
Metrics
- CVSS 3.1
-
7.4
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:N/A:N - EPSS — exploit probability
- 0% percentile: 41 · as of 8 November 2026
- CWE
- CWE-346CWE-942
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.