Improper Signature Verification in Hyper-MCP Affects WebAssembly Plugins

CVE-2026-108699

What is CVE-2026-108699?

The Hyper-MCP tool, up to version 0.8.3, is exposed to an improper signature verification vulnerability that permits malicious actors to load harmful WebAssembly plugins. This occurs because the cosign_verify_args() function accepts any signer identity and OIDC issuer by default. Attackers can exploit this flaw by controlling a plugin image reference, allowing them to sign a malicious image with a free Sigstore keyless certificate. Once executed, these plugins can operate with full access to the host, filesystem, and environment capabilities, posing significant security risks to users.

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