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

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.4%

EPSS score, percentile 29.7 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

5.3 Medium

CVSS v4.0 base score, given by the CNA

What should I do?

The vulnerability is remediated by applying HTML entity encoding to the count field value before it is rendered in the view template. Full textSolution from the CVE record.

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (1)

Which versions are affected?

Affected

• before 2.5.48

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Solution (from the CVE record)

The vulnerability is remediated by applying HTML entity encoding to the count field value before it is rendered in the view template. This ensures that any HTML or script markup contained in the value from a remote server is neutralized and displayed as inert text rather than being interpreted by the browser.

Advisories and patches

• Security patch (Patch)

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

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 us…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-104900 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 2 Oct 2026.
• The CVE record carries a CVSS v4.0 base score of 5.3 (Medium), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.4% (percentile 29.7), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
• The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

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.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline