# CVE-2026-15791: LLB file operation can be tricked to remove /tmp directory contents

> Attackers can use crafted BuildKit API messages to delete host /tmp contents via path traversal, impacting container infrastructure security.

- **Severity:** Low 3.3 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 21 Jul 2026
- **Updated:** 21 Jul 2026
- **Also known as:** GHSA-32pv-7hq5-qhwq, UBUNTU-CVE-2026-15791

## What is CVE-2026-15791?

CVE-2026-15791 is a low-severity path traversal vulnerability in moby BuildKit, published on 21 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

A crafted message in the BuildKit low-level build API can be used to remove the contents of the /tmp directory. The action that can normally be used to delete files inside the build container rootfs can escape into the real host temp directory.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-15791?

It affects 1 product.


Products: Mobyproject Buildkit.

## How do I fix CVE-2026-15791?

No fix has been published for CVE-2026-15791 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-15791 being exploited?

There is no known exploitation of CVE-2026-15791 in the wild and no public exploit code.

## Other vulnerabilities in moby BuildKit

- [CVE-2024-23652](https://insights.sbomify.com/CVE-2024-23652/): BuildKit possible host system access from mount stub cleaner (critical 10.0)
- [CVE-2024-23653](https://insights.sbomify.com/CVE-2024-23653/): BuildKit interactive containers API does not validate entitlements check (critical 9.8)
- [CVE-2024-23651](https://insights.sbomify.com/CVE-2024-23651/): BuildKit possible race condition with accessing subpaths from cache mounts (high 8.7)
- [CVE-2026-33747](https://insights.sbomify.com/CVE-2026-33747/): BuildKit vulnerable to malicious frontend causing file escape outside of storage root (high 8.4)
- [CVE-2026-33748](https://insights.sbomify.com/CVE-2026-33748/): BuildKit Git URL subdir component can cause access to restricted files (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-15791 and fix it if it is affected.

What it is: CVE-2026-15791 is a low-severity path traversal vulnerability in moby BuildKit, published on 21 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-15791 in the wild and no public exploit code.

Affected product: moby BuildKit. 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-2026-15791/ (Markdown: https://insights.sbomify.com/CVE-2026-15791/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-15791
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15791
- OSV: https://osv.dev/vulnerability/CVE-2026-15791

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-15791/
Summaries are generated and may contain mistakes; the official description above is the record.