Vulnerability · Published Oct 11, 2026 · Assigned by VulnCheck

CVE-2026-108698hyper-mcp through 0.8.3 OCI Plugin Signature Verification TOCTOU Race Condition

Medium 6.5

In plain English

A medium-severity security flaw in hyper-mcp from hyper-mcp-rs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 16% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.2%top 84.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

hyper-mcp through 0.8.3 contains a signature verification bypass vulnerability in load_wasm in src/wasm/oci.rs that verifies the Cosign signature of a separately resolved tag rather than the loaded manifest. Attackers controlling registry responses for the tag can serve an unsigned malicious manifest to the loader and a signed one to Cosign, executing unsigned WebAssembly plugins with configured host capabilities.

Affected products (as reported)

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

Weakness: CWE-367 · 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#L79-L148 technical-description
https://github.com/hyper-mcp-rs/hyper-mcp/blob/v0.8.3/src/wasm/oci.rs#L193-L224 technical-description
https://github.com/hyper-mcp-rs/hyper-mcp product
VulnCheck Advisory: hyper-mcp through 0.8.3 OCI Plugin Signature Verification TOCTOU Race Condition third-party-advisory