# CVE-2026-93321: Malformed LLB file operation can crash buildkitd

> A malicious frontend can submit a malformed LLB definition to crash the BuildKit daemon, disrupting all active builds.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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:** Not needed
- **Fix available:** Yes
- **Published:** 5 Oct 2026
- **Updated:** 6 Oct 2026
- **Also known as:** AZL-106821, BELL-CVE-2026-93321, GHSA-fjj4-h6vf-m9hj, UBUNTU-CVE-2026-93321

## What is CVE-2026-93321?

CVE-2026-93321 is a medium-severity denial of service vulnerability in moby BuildKit, published on 5 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A malicious frontend can submit an LLB definition that causes buildkitd
to panic and terminate, interrupting all builds running on that daemon.

Weakness: CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2026-93321?


## How do I fix CVE-2026-93321?

Apply the vendor's patch.

## Is CVE-2026-93321 being exploited?

There is no known exploitation of CVE-2026-93321 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93321 and fix it if it is affected.

What it is: CVE-2026-93321 is a medium-severity denial of service vulnerability in moby BuildKit, published on 5 Oct 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-2026-93321 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-2026-93321/ (Markdown: https://insights.sbomify.com/CVE-2026-93321/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93321
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93321
- OSV: https://osv.dev/vulnerability/CVE-2026-93321

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93321/
Summaries are generated and may contain mistakes; the official description above is the record.