# CVE-2026-108699: hyper-mcp through 0.8.3 Improper Signature Verification of OCI WebAssembly Plugins

> Attackers can execute malicious WebAssembly plugins by bypassing signature verification in hyper-mcp, leading to arbitrary code execution with host capabilities.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/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:** 11 Oct 2026
- **Updated:** 13 Oct 2026
- **Also known as:** GHSA-4j25-h357-wg62

## What is CVE-2026-108699?

CVE-2026-108699 is a high-severity vulnerability in hyper-mcp-rs hyper-mcp, published on 11 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

hyper-mcp through 0.8.3 contains an improper signature verification vulnerability that allows attackers to load malicious WebAssembly plugins because cosign_verify_args() accepts any signer identity and OIDC issuer by default. Attackers controlling a plugin image reference can sign a malicious image with a free Sigstore keyless certificate to execute plugins with configured host, filesystem, and environment capabilities.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-108699?


## How do I fix CVE-2026-108699?

No fix has been published for CVE-2026-108699 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-108699 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-108699 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-108699 and fix it if it is affected.

What it is: CVE-2026-108699 is a high-severity vulnerability in hyper-mcp-rs hyper-mcp, published on 11 Oct 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-2026-108699 exists.

Affected product: hyper-mcp-rs hyper-mcp. 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-2026-108699/ (Markdown: https://insights.sbomify.com/CVE-2026-108699/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-108699
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-108699
- OSV: https://osv.dev/vulnerability/CVE-2026-108699

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-108699/
Summaries are generated and may contain mistakes; the official description above is the record.