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

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-11 · updated 2026-10-16
Weakness: CWE-367

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

hyper-mcp-rs hyper-mcp: through 0.8.3

References

https://github.com/hyper-mcp-rs/hyper-mcp
https://github.com/hyper-mcp-rs/hyper-mcp/blob/v0.8.3/src/wasm/oci.rs#L193-L224
https://github.com/hyper-mcp-rs/hyper-mcp/blob/v0.8.3/src/wasm/oci.rs#L79-L148
https://hackmd.io/@1ExmmukzRMWN7B4gQ4W-4Q/hyper-mcp-oci-signature-manifest-toctou
https://www.vulncheck.com/advisories/hyper-mcp-through-0.8.3-oci-plugin-signature-verification-toctou-race-condition

Get alerted when CVE-2026-108698 or the next vulnerability affects your stack