TOCTOU race in hyper-mcp lets attackers load unsigned plugins
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- Low · High · None
- Fix status
- No fix listed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
Summary
hyper-mcp through 0.8.3 checks the Cosign signature of a separately resolved tag instead of the manifest it loads (CWE-367). A remote attacker who controls registry responses for that tag can serve an unsigned malicious manifest to the loader while serving a signed one to Cosign, so unsigned WebAssembly plugins run with the configured host capabilities.
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| hyper-mcp-rs | hyper-mcp | up to 0.8.3 | — | No fix listed | CNA |
- hyper-mcp Vendorhyper-mcp-rs Affected up to 0.8.3 Fixed in — No fix listed CNA
Remediation
The sources list no fixed version for hyper-mcp.
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
Timeline
- 2026-10-11 Threatist record created from CVE-2026-108698
- 2026-10-11 Alias added: GHSA-phv4-c98f-77h3
- 2026-10-12 Priority changed: MEDIUM → LOW
- 2026-10-13 CISA SSVC decision points changed
References
More hyper-mcp-rs vulnerabilities
- TI-2026-70679 hyper-mcp loads WebAssembly plugins without proper signature verification CVSS 4.0HIGH 8.3
Sources
- CVE-2026-108698 · CVE Program
- CVE-2026-108698 · NVD
- FIRST EPSS
- GHSA-phv4-c98f-77h3 · GitHub Advisory Database · CC BY 4.0
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