# CVE-2026-88064: Backstage: Improper input validation in TechDocs MkDocs configuration

> Authenticated users can execute arbitrary code via unsafe YAML tags in TechDocs configuration, impacting the backend container resources.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 16 Sep 2026
- **Updated:** 16 Sep 2026
- **Also known as:** GHSA-292q-8mf5-h6g3

## What is CVE-2026-88064?

CVE-2026-88064 is a high-severity code injection vulnerability in Linuxfoundation Backstage, published on 16 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Backstage is an open framework for building developer portals. Prior to 1.14.6 and from 1.15.0 until 1.15.4, the @backstage/plugin-techdocs-node package insufficiently validates mkdocs.yml supplied by an authenticated user who can register or modify a TechDocs source. Unsafe Python YAML tags, markdown_extensions names and configuration, theme options, and extra_templates values can reach the documentation generator and cause unintended code execution. The resulting impact is limited to the files, credentials, network access, and other resources available to the TechDocs backend or build container. This issue is fixed in versions 1.14.6 and 1.15.4.

Weakness: CWE-20 (Improper Input Validation), CWE-1336 (Improper Neutralization of Special Elements Used in a Template Engine)

## Which versions are affected by CVE-2026-88064?

It affects 2 products.


Products: Linuxfoundation Backstage, Linuxfoundation Backstage Plugin-Techdocs-Node.

## How do I fix CVE-2026-88064?

No fix has been published for CVE-2026-88064 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-88064 being exploited?

There is no known exploitation of CVE-2026-88064 in the wild and no public exploit code.

## Other vulnerabilities in Linuxfoundation Backstage

- [CVE-2026-106501](https://insights.sbomify.com/CVE-2026-106501/): Backstage: Sensitive information exposure in Scaffolder (critical 9.6)
- [CVE-2026-106558](https://insights.sbomify.com/CVE-2026-106558/): Backstage: Improper validation of TechDocs MkDocs configuration (high 8.8)
- [CVE-2026-106459](https://insights.sbomify.com/CVE-2026-106459/): Backstage: Improper input validation in Sentry scaffolder actions (high 8.5)
- [CVE-2026-106486](https://insights.sbomify.com/CVE-2026-106486/): Backstage: Improper filesystem validation in Bitbucket pull-request scaffolder actions (high 8.5)
- [CVE-2026-106500](https://insights.sbomify.com/CVE-2026-106500/): Backstage: Improper task state validation in Scaffolder backend (high 8.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-88064 and fix it if it is affected.

What it is: CVE-2026-88064 is a high-severity code injection vulnerability in Linuxfoundation Backstage, published on 16 Sep 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-2026-88064 in the wild and no public exploit code.

Affected product: Linuxfoundation Backstage. 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-2026-88064/ (Markdown: https://insights.sbomify.com/CVE-2026-88064/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88064
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88064
- OSV: https://osv.dev/vulnerability/CVE-2026-88064

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-88064/
Summaries are generated and may contain mistakes; the official description above is the record.