CVE-2026-104900: MISP Stored XSS via Unescaped Count Field Value in Remote Event Preview Index
MISP contains a stored cross-site scripting (XSS) vulnerability in the index table rendering of the remote event preview. The count field template escaped the associated link URL but rendered the field value without HTML encoding. An attacker with the ability to create or modify events on a linked (remote) MISP server could craft an event identifier containing HTML or JavaScript markup. When a user on the local MISP instance views the remote event preview index, the unescaped value is rendered directly in the browser, allowing arbitrary script execution in the victim's session.
Preconditions:
- A linked/remote MISP server is configured and connected to the local instance.
- The attacker has sufficient access on the linked server to create or modify an event with a crafted identifier.
- A victim user on the local instance views the remote event preview index page.
Impact:
- Execution of arbitrary JavaScript in the context of the MISP web application.
- Potential session hijacking, data exfiltration, or unauthorized actions performed on behalf of the authenticated user.
Affected versions: <2.5.48.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
MISPto a version that resolves this vulnerability.Fixed in 2.5.48
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Affected deployments are MISP versions earlier than 2.5.48 that have a linked and connected remote MISP server. The vulnerable rendering is reached when users view the remote event preview index on the local instance.
What access does an attacker need to exploit it?
The attacker needs sufficient permissions on the linked remote MISP server to create or modify an event. They must set a crafted event identifier containing HTML or JavaScript markup, and a user on the local instance must subsequently open the remote event preview index.
Are default standalone MISP deployments affected?
The described attack requires a linked remote MISP server and does not apply through the stated path to a standalone instance without a connected remote server. It also requires a local user to view the remote event preview index.
How can administrators determine whether they may already be affected?
Check whether the local MISP instance is running a version earlier than 2.5.48 and has connected remote MISP instances. Review events on linked servers, particularly event identifiers, for unexpected HTML or JavaScript-like markup, and consider whether local users have viewed the remote event preview index.
What can be done if updating is not immediately possible?
Reduce exposure by disabling or avoiding use of the remote event preview index and restricting who can create or modify events on linked remote MISP servers. Review trust relationships with connected instances and remove or isolate remote connections that are not required.