# CVE-2026-81820: Flowintel HTML Injection in MISP Case History Timeline via Crafted Object Attributes

> Attackers can inject malicious HTML into MISP case timelines via crafted object attributes, potentially leading to script execution or UI manipulation.

- **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:** 27 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** GHSA-cv7j-9q69-fxh4

## What is CVE-2026-81820?

CVE-2026-81820 is a medium-severity cross-site scripting vulnerability in flowintel, published on 27 Aug 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

Affected versions of Flowintel construct timeline HTML using attacker-controllable MISP object fields such as:

  *  
object UUID;

  *  
object name;

  *  
attribute value;

  *  
attribute type;

  *  
comment;

  *  
first/last seen values;

  *  
IDS flag.

Those values were concatenated directly into HTML strings before rendering. The upstream commit explicitly states that DOMPurify removed XSS vectors but still allowed other HTML elements, such as forms, through.

The fix replaces direct string interpolation with DOM construction via document.createElement() and assigns all attacker-controlled values using textContent. The headline is similarly converted to escaped HTML through a temporary element.

Version impacted =>3.3.0

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

## Which versions are affected by CVE-2026-81820?


## How do I fix CVE-2026-81820?

No fix has been published for CVE-2026-81820 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81820 being exploited?

There is no known exploitation of CVE-2026-81820 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81820 and fix it if it is affected.

What it is: CVE-2026-81820 is a medium-severity cross-site scripting vulnerability in flowintel, published on 27 Aug 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-2026-81820 in the wild and no public exploit code.

Affected product: flowintel. 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-2026-81820/ (Markdown: https://insights.sbomify.com/CVE-2026-81820/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81820
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81820
- OSV: https://osv.dev/vulnerability/CVE-2026-81820

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81820/
Summaries are generated and may contain mistakes; the official description above is the record.