# CVE-2026-18171: Docker Sandboxes read-only runtime mount writable through its shared-export alias

> Unprivileged code in Docker Sandboxes can write to host directories intended to be read-only by exploiting a shared-export alias vulnerability.

- **Severity:** Medium 5.7 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 12 Aug 2026
- **Updated:** 12 Aug 2026
- **Also known as:** GHSA-q3q4-c92f-m955

## What is CVE-2026-18171?

CVE-2026-18171 is a medium-severity missing authorization vulnerability in Docker Sandboxes, published on 12 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Docker Sandboxes (sbx) applies the read-only intent of a runtime host mount to the in-guest container bind only: the underlying virtio-fs host-edge grant is added to the sandbox's policy-share allowlist with no access mode. The directory stays writable at its shared-export path, so unprivileged code inside the sandbox can derive that path and write to a host directory the operator attached read-only.

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-18171?


## How do I fix CVE-2026-18171?

No fix has been published for CVE-2026-18171 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-18171 being exploited?

There is no known exploitation of CVE-2026-18171 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-18171 and fix it if it is affected.

What it is: CVE-2026-18171 is a medium-severity missing authorization vulnerability in Docker Sandboxes, published on 12 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-18171 in the wild and no public exploit code.

Affected product: Docker Sandboxes. 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-2026-18171/ (Markdown: https://insights.sbomify.com/CVE-2026-18171/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-18171
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-18171
- OSV: https://osv.dev/vulnerability/CVE-2026-18171

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-18171/
Summaries are generated and may contain mistakes; the official description above is the record.