CVE-2026-104900: MISP Stored XSS via Unescaped Count Field Value in Remote Event Preview Index

Severity: medium (CVSS 5.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-02 · updated 2026-10-02
Weakness: CWE-79

Description

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 products

MISP: before 2.5.48 — fixed in 2.5.48

How to fix

Upgrade to a fixed version: MISP 2.5.48. Check the vendor advisory for mitigations.

References

https://github.com/MISP/MISP/commit/2a2981a27

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