Unauthenticated command execution in Flyto2 Core over HTTP MCP
Key facts
- Attack vector
- Local
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass, Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-306 and CWE-78.
Summary
Flyto2 Core versions from 2.26.2 before 2.26.4 expose the HTTP MCP POST /mcp route without the authentication check used by the REST execution routes. An unauthenticated attacker can call the execute_module tool to run shell commands through sandbox.execute_shell with the privileges of the flyto-core server process. The route is reachable locally under the default loopback binding and over the network when the server binds to a non-loopback interface. The flaw is missing authentication for a critical function (CWE-306).
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
Description from the CNA
Flyto2 Core is an execution kernel for automation and AI-agent workflows. From 2.26.2 until 2.26.4, the HTTP MCP POST /mcp route accepts unauthenticated JSON-RPC tools/call requests and forwards execute_module arguments to the module registry without the require_auth dependency used by the REST execution routes. An unauthenticated caller can select sandbox.execute_shell and supply its command parameter, which reaches asyncio.create_subprocess_shell with the privileges of the flyto-core server process. The endpoint is reachable locally under the default loopback binding and becomes network reachable when an operator binds the server to a non-loopback interface, allowing arbitrary OS command execution and potential full host compromise. This issue is fixed in version 2.26.4.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Total
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 |
|---|---|---|---|---|---|
| flytohub | flyto-core | 2.26.2 to before 2.26.4 | 2.26.4 | Patch available | CNA |
| — | flyto-core (PyPI) | 2.26.2 to before 2.26.4 | 2.26.4 | Patch available | GHSA-h9f9-h6gm-wc85 |
- flyto-core Vendorflytohub Affected 2.26.2 to before 2.26.4 Fixed in 2.26.4 Patch available CNA
- flyto-core (PyPI) Vendor— Affected 2.26.2 to before 2.26.4 Fixed in 2.26.4 Patch available GHSA-h9f9-h6gm-wc85
Remediation
Upgrade the PyPI package flyto-core to version 2.26.4, which fixes the issue.
Written with Claude Haiku 5.5 from the sources below · 2026-10-29
- Fix · CNA flyto-core (flytohub) Fixed in 2.26.4
- Fix · GHSA-h9f9-h6gm-wc85 flyto-core (PyPI) Fixed in 2.26.4 Advisory →
Timeline
- 2026-10-15 Threatist record created from CVE-2026-55786
- 2026-10-15 Alias added: GHSA-h9f9-h6gm-wc85
- 2026-10-16 Priority changed: MEDIUM → LOW
- 2026-10-29 CISA SSVC decision points changed
- 2026-10-29 Priority changed: LOW → HIGH
References
Other 5
- https://github.com/flytohub/flyto-core/security/advisories/GHSA-h9f9-h6gm-wc85
- https://github.com/flytohub/flyto-core/commit/db7f116b1d3c5dcf94aded00d14118f81f3e225e
- https://github.com/flytohub/flyto-core/releases/tag/v2.26.4
- https://github.com/flytohub/flyto-core
- https://github.com/pypa/advisory-database/tree/main/vulns/flyto-core/PYSEC-2026-2482.yaml
More flytohub vulnerabilities
- TI-2026-47709 Flyto2 Core: Arbitrary file write via image.download (and other file-writing modules) CVSS 3.1CRITICAL 10.0
- TI-2026-47706 Flyto2 Core: Unauthenticated flyto-verification /run: callback_url SSRF and internal runner-secret exfiltration CVSS 3.1CRITICAL 9.3
- TI-2026-47707 Flyto2 Core: ${env.VAR} interpolation reads any env secret despite env.get being denylisted CVSS 3.1HIGH 8.6
- TI-2026-47705 Flyto2 Core: LLM/API keys leak to an attacker-controlled base_url CVSS 3.1HIGH 8.6
- TI-2026-47708 Server-side request forgery in flytohub flyto-core CVSS 3.1HIGH 8.5
- TI-2026-47704 Flyto2 Core: Guarded HTTP modules follow redirects into internal space without per-hop SSRF revalidation CVSS 3.1HIGH 8.5
Sources
- CVE-2026-55786 · CVE Program
- CVE-2026-55786 · NVD
- FIRST EPSS
- GHSA-h9f9-h6gm-wc85 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences