# CVE-2026-39866: Lawnchair vulnerable to Command Injection via unquoted workflow dispatch input in release_update.yml

> Command injection in the release workflow allows arbitrary code execution, requiring a patch to secure the build process.

- **Severity:** High 7.4 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P`)
- **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:** 21 Apr 2026
- **Updated:** 25 Apr 2026
- **Also known as:** GHSA-9prc-pp2c-3427

## What is CVE-2026-39866?

CVE-2026-39866 is a high-severity command injection vulnerability in LawnchairLauncher lawnchair, published on 21 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Lawnchair is a free, open-source home app for Android. Prior to commit fcba413f55dd47f8a3921445252849126c6266b2, command injection in release_update.yml workflow dispatch input allows arbitrary code execution. Commit fcba413f55dd47f8a3921445252849126c6266b2 patches the issue.

Weakness: CWE-77 (Improper Neutralization of Special Elements used in a Command)

## Which versions are affected by CVE-2026-39866?

It affects 1 product.


Products: Lawnchair Lawnchair.

## How do I fix CVE-2026-39866?

No fix has been published for CVE-2026-39866 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-39866 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39866 exists.

Public exploit code:

- Authorized security-research lab: reproduction of CVE-2026-39866 (GHSA-9prc-pp2c-3427) — workflow_dispatch input template injection in .github/workflows/release_update.yml of LawnchairLauncher/lawnchair @ b089bae8c007f36a8ce0346725182a107d97cd05. Snapshot pinned to the vulnerable commit; owner-gated sign-info step retargeted for the lab. (github_poc): https://github.com/pvharmo2/gha-lab-360f77d0d4
- https://github.com/abhayclasher/CVE-2026-39866 (github_poc): https://github.com/abhayclasher/CVE-2026-39866

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39866 and fix it if it is affected.

What it is: CVE-2026-39866 is a high-severity command injection vulnerability in LawnchairLauncher lawnchair, published on 21 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-39866 exists.

Affected product: LawnchairLauncher lawnchair. 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-2026-39866/ (Markdown: https://insights.sbomify.com/CVE-2026-39866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39866
- OSV: https://osv.dev/vulnerability/CVE-2026-39866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39866/
Summaries are generated and may contain mistakes; the official description above is the record.