ollama - 💡(How to fix) Fix [MEDIUM] Overly permissive CORS configuration allows wildcard origins

Severity: MEDIUM -- CVSS 5.3

Location: server/routes.go (GenerateRoutes), envconfig/config.go (AllowedOrigins) Category: CORS Misconfiguration Confidence: Certain CWE: CWE-942 MITRE ATT&CK: T1090.001, T1213

Description

The CORS configuration is highly permissive. The server sets AllowWildcard = true and the default AllowedOrigins() includes port wildcards and dangerous origins:

"http://127.0.0.1:*",      // PORT WILDCARD
"https://127.0.0.1:*",     // PORT WILDCARD
"http://0.0.0.0:*",        // PORT WILDCARD
"https://0.0.0.0:*",       // PORT WILDCARD
"app://*",
"file://*",                // ANY local HTML file
"tauri://*",
"vscode-webview://*",
"vscode-file://*",

Key concerns:

1. Port wildcard * -- any local port is accepted as a valid CORS origin
2. file://* -- any local HTML file opened in a browser can make cross-origin requests to the ollama API
3. AllowWildcard = true combined with custom origins -- browser behavior can be unpredictable across versions

Impact

• A local HTML file with embedded JavaScript (opened from downloads, email attachment) can make requests to the ollama API
• Malicious browser extensions or Electron apps can exploit the permissive CORS to interact with ollama
• Combined with the "no auth by default" finding, this enables silent model abuse from any local webpage

Remediation

1. Remove port wildcards -- specify exact ports or use 127.0.0.1 without port
2. Remove file://* origin -- it is almost never needed legitimately
3. Set AllowWildcard = false when custom origins are specified
4. Document that OLLAMA_ORIGINS should be set to specific origins in production

Found as part of a broader security audit of ollama/ollama.