T09 · Insecure Skill Coding Practices
- Location
SKILL.md:191- Finding
Unauthenticated Ollama API Exposed on All Network Interfaces
- Content
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Vulnerability Details
File Location:
SKILL.md, lines 191–194
Vulnerability Type: Unauthenticated network service exposure
Risk Level: HighVulnerable Code Snippet:
bash # Check whether the service is operating normally through the API curl http://localhost:11434/api/tags # ... # Configure the service listening address to allow LAN access OLLAMA_HOST=0.0.0.0:11434 ollama serveThe security-relevant context at line 252 states that the Ollama service requires no authentication by default:
text The Ollama service listens on localhost:11434 by default and requires no authentication.Technical Analysis
The Skill recommends setting
OLLAMA_HOST=0.0.0.0:11434, which causes Ollama to listen on every available network interface instead of only the loopback interface. The document also acknowledges that the service has no authentication by default.Combining an all-interface bind address with an unauthenticated API creates an externally reachable service whenever host or network firewall rules permit traffic to TCP port 11434. Although the Skill later recommends restricting access with firewall rules, the demonstrated command does not require those controls to be established before exposure occurs and does not place the service behind authentication or transport encryption.
A remote party capable of reaching port 11434 may submit requests to the API functions supported by the installed Ollama version. This can permit model enumeration, inference requests, resource-intensive operations, and interaction with available model-management endpoints.
Attack Path
- A user follows the service-management example and runs:
bash OLLAMA_HOST=0.0.0.0:11434 ollama serve - Ollama begins listening on port 11434 across all host interfaces without application-level authentication.
- The host is connected to a LAN or another network where an untrusted party can reach that ...[truncated 1491 chars]
- A user follows the service-management example and runs:
- Remediation
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Remediation Suggestions
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Keep Ollama bound to the loopback interface by default:
bash OLLAMA_HOST=127.0.0.1:11434 ollama serve -
Remove the unconditional
0.0.0.0example or mark it as unsafe unless all prerequisite controls have already been applied. -
If remote access is required, place Ollama behind a hardened reverse proxy that provides:
- Strong authentication and authorization.
- TLS encryption.
- Request-size and rate limits.
- Connection and execution timeouts.
- Access logging and monitoring.
- Restrictions on model-management endpoints.
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Configure host and network firewalls before changing the bind address. Permit TCP port 11434 only from explicitly trusted source addresses or private management networks.
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Require explicit user confirmation before the Agent starts a network-accessible service, and clearly report the selected bind address and lack of native authentication.
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Run Ollama under a dedicated, unprivileged operating-system account with limited filesystem access and resource quotas.
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Prefer a VPN or authenticated tunnel rather than exposing the API directly to a LAN or the public Internet.
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Add verification steps after startup to confirm that the service is not reachable from unauthorized interfaces or hosts.
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