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

> Stored XSS in MISP allows attackers to execute arbitrary JavaScript in victim sessions via crafted remote event identifiers.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 2 Oct 2026
- **Updated:** 2 Oct 2026
- **Also known as:** GHSA-7mf5-g482-f646

## What is CVE-2026-104900?

CVE-2026-104900 is a medium-severity cross-site scripting vulnerability in MISP, published on 2 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-104900?


## How do I fix CVE-2026-104900?

No fix has been published for CVE-2026-104900 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-104900 being exploited?

There is no known exploitation of CVE-2026-104900 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104900 and fix it if it is affected.

What it is: CVE-2026-104900 is a medium-severity cross-site scripting vulnerability in MISP, published on 2 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-104900 in the wild and no public exploit code.

Affected product: MISP. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-104900/ (Markdown: https://insights.sbomify.com/CVE-2026-104900/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104900
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104900
- OSV: https://osv.dev/vulnerability/CVE-2026-104900

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104900/
Summaries are generated and may contain mistakes; the official description above is the record.