# CVE-2026-88921: MISP: Unescaped HTML Injection in PDF Report Element Rendering

> Authenticated users can inject HTML into MISP PDF reports, potentially executing scripts or altering document integrity during export.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 10 Sep 2026
- **Updated:** 10 Sep 2026
- **Also known as:** GHSA-6h22-87v4-49wc

## What is CVE-2026-88921?

CVE-2026-88921 is a medium-severity cross-site scripting vulnerability in MISP, published on 10 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

MISP contains an HTML injection vulnerability in the MISPElementHTMLFormatterTool component, which is responsible for rendering MISP element references (attributes, objects, and tags) into inline HTML during PDF report export via the convert_markdown_to_pdf module. The attribute(), objectAttribute(), object(), and tag() methods interpolated user-controlled fields (attribute type, attribute value, object name, object relation, tag name, tag colour, and tag text colour) directly into HTML templates without applying HTML entity encoding. An authenticated user with the ability to create or modify MISP attributes, objects, or tags could embed arbitrary HTML markup in these fields. When a report containing such elements was exported to PDF, the unescaped content was rendered as live HTML rather than inert text, potentially injecting script tags, breaking the document structure, or altering the visual content of the exported report. Additionally, the attribute() method contained a template with hardcoded sample values ("domain-ip" and "google.com") instead of format placeholders, meaning every plain attribute reference in a PDF displayed the sample text rather than the actual indicator value, constituting a data-integrity defect in the exported document. The vulnerability requires an authenticated actor with write access to MISP elements and a subsequent PDF export of a report referencing those elements. The security impact is primarily to the integrity of the exported document and, depending on the HTML-to-PDF rendering engine, potential execution of injected markup during the conversion step.

Version affected: ≤2.5.45

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2026-88921?


## How do I fix CVE-2026-88921?

No fix has been published for CVE-2026-88921 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-88921 being exploited?

There is no known exploitation of CVE-2026-88921 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-88921 and fix it if it is affected.

What it is: CVE-2026-88921 is a medium-severity cross-site scripting vulnerability in MISP, published on 10 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-88921 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-2026-88921/ (Markdown: https://insights.sbomify.com/CVE-2026-88921/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88921
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88921
- OSV: https://osv.dev/vulnerability/CVE-2026-88921

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-88921/
Summaries are generated and may contain mistakes; the official description above is the record.