MISP's REST detection can be influenced by request properties such as the URL suffix or the HTTP Accept header. Because Accept: application/json can be supplied by a cross-origin page without requiring a CORS preflight, an attacker could cause a request originating from another website to be treated as REST traffic. MISP would consequently disable its normal form-security and CSRF validation even though the request was authenticated using the victim's existing browser session.
An unauthenticated remote attacker could exploit this behavior by convincing an authenticated MISP user to visit or interact with a malicious web page. The attacker's page could then issue crafted requests to susceptible state-changing MISP endpoints using the victim's privileges. Depending on the permissions of the victim and the targeted endpoint, this could allow unauthorized modification, creation, publication, or removal of data and other state changes.
The vulnerability originates from granting the form-security exemption based on _isRest() rather than on the authentication mechanism used by the request. The patch changes this behavior so that CSRF and form-security exemptions are granted only when the request actually carries a MISP API key. Session-authenticated REST-style requests remain subject to CSRF protection.
The fix also introduces support for transmitting CSRF tokens through the X-CSRF-Token header for legitimate same-origin AJAX requests. Such a header cannot normally be attached by a cross-origin page without triggering a CORS preflight, preventing it from being used to reproduce the original attack.
Analysis and contextual insights are available on OpenCVE Cloud.
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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| Link | Providers |
|---|---|
| https://github.com/MISP/MISP/commit/f82646727 |
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Fri, 04 Sep 2026 17:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
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Fri, 04 Sep 2026 10:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Misp
Misp misp |
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| Vendors & Products |
Misp
Misp misp |
Fri, 04 Sep 2026 09:45:00 +0000
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| Description | A cross-site request forgery (CSRF) vulnerability exists in MISP due to form-security and CSRF protections being disabled based on whether an incoming request was identified as a REST request. MISP's REST detection can be influenced by request properties such as the URL suffix or the HTTP Accept header. Because Accept: application/json can be supplied by a cross-origin page without requiring a CORS preflight, an attacker could cause a request originating from another website to be treated as REST traffic. MISP would consequently disable its normal form-security and CSRF validation even though the request was authenticated using the victim's existing browser session. An unauthenticated remote attacker could exploit this behavior by convincing an authenticated MISP user to visit or interact with a malicious web page. The attacker's page could then issue crafted requests to susceptible state-changing MISP endpoints using the victim's privileges. Depending on the permissions of the victim and the targeted endpoint, this could allow unauthorized modification, creation, publication, or removal of data and other state changes. The vulnerability originates from granting the form-security exemption based on _isRest() rather than on the authentication mechanism used by the request. The patch changes this behavior so that CSRF and form-security exemptions are granted only when the request actually carries a MISP API key. Session-authenticated REST-style requests remain subject to CSRF protection. The fix also introduces support for transmitting CSRF tokens through the X-CSRF-Token header for legitimate same-origin AJAX requests. Such a header cannot normally be attached by a cross-origin page without triggering a CORS preflight, preventing it from being used to reproduce the original attack. | |
| Title | Cross-Site Request Forgery via Attacker-Controlled REST Detection in MISP | |
| Weaknesses | CWE-352 | |
| References |
| |
| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: CIRCL
Published:
Updated: 2026-09-04T16:30:58.514Z
Reserved: 2026-09-04T09:40:50.773Z
Link: CVE-2026-85547
Updated: 2026-09-04T16:30:41.358Z
Status : Received
Published: 2026-09-04T10:17:14.433
Modified: 2026-09-04T17:17:03.503
Link: CVE-2026-85547
No data.
OpenCVE Enrichment
Updated: 2026-09-04T10:30:17Z
-
CWE-352
Cross-Site Request Forgery (CSRF)