Vulnerability · Published Oct 11, 2026 · Assigned by VulnCheck

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

Medium 6.5

In plain English

A medium-severity security flaw in hyper-mcp from hyper-mcp-rs. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 6% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.2%top 93.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

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.

Affected products (as reported)

Vendor	Product	Versions
hyper-mcp-rs	hyper-mcp	0 – through 0.8.3

Weakness: CWE-347 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

References

https://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/hyper-mcp-oci-signature-manifest-toctou third-party-advisory
https://github.com/hyper-mcp-rs/hyper-mcp/blob/v0.8.3/src/wasm/oci.rs#L157-L190 technical-description
https://github.com/hyper-mcp-rs/hyper-mcp/blob/v0.8.3/src/config.rs#L138-L170 technical-description
https://github.com/hyper-mcp-rs/hyper-mcp product
VulnCheck Advisory: hyper-mcp through 0.8.3 Improper Signature Verification of OCI WebAssembly Plugins third-party-advisory
https://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/cve-2026-108698-108699-hyper-mcp-oci-signature-manifest-toctou exploit