# CVE-2026-67531: FrontMCP: CodeCall sandbox escape -> host RCE via live Zod schema exposure by getTool

> FrontMCP allows sandbox escape and remote code execution via exposed Zod schemas, enabling attackers to steal secrets and execute arbitrary code.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Aug 2026
- **Updated:** 6 Aug 2026
- **Also known as:** GHSA-mp29-fxh8-92px

## What is CVE-2026-67531?

CVE-2026-67531 is a critical code injection vulnerability in agentfront frontmcp, published on 5 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

FrontMCP is a TypeScript-first framework for the Model Context Protocol (MCP). Prior to 1.5.7, the sandboxed codecall:execute tool exposes live host Zod schema instances to the script via getTool(), and because Zod v4 defines _zod as a non-configurable, non-writable own property, the ECMAScript Proxy invariants force the security membrane to hand back the raw host object, letting a script reach _zod.constr.constructor (the host Function constructor) and execute arbitrary code in the server process. A single tools/call is sufficient to escape the sandbox and achieve remote code execution as the server user, exposing everything the process holds such as OAuth client secrets, JWT_SECRET, session keys, database credentials, and cloud instance metadata. Because the framework's DEFAULT_AUTH_OPTIONS is public mode, an unconfigured server serves this to unauthenticated callers, and on authenticated servers an indirect prompt injection in tool output or fetched content can trigger it without a human attackerThis issue is fixed in version 1.5.7.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-67531?


## How do I fix CVE-2026-67531?

No fix has been published for CVE-2026-67531 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-67531 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67531 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-67531 and fix it if it is affected.

What it is: CVE-2026-67531 is a critical code injection vulnerability in agentfront frontmcp, published on 5 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-67531 exists.

Affected product: agentfront frontmcp. 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-2026-67531/ (Markdown: https://insights.sbomify.com/CVE-2026-67531/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-67531
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-67531
- OSV: https://osv.dev/vulnerability/CVE-2026-67531

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-67531/
Summaries are generated and may contain mistakes; the official description above is the record.