R2.5: Outbound SSRF & timeout guard

Short answer: Validate URL host and set AbortSignal.timeout(). A server that fetches any URL can be pointed at your internal network, and a call with no limit can hang.

Group: Security and tenancy. Status: stable. Generated from the rule definitions; do not edit by hand.

Playground: https://brevio.pro/tools/agent-guard-playground?rule=R2.5

What it catches

Outbound SSRF & timeout guard: validate URL host and set AbortSignal.timeout().

Why

A server that fetches any URL can be pointed at your internal network, and a call with no limit can hang.

A bad example

const res = await fetch(req.query.url);

A good example

const url = new URL(input);
if (!ALLOWED.has(url.host)) throw new Error('host');
await fetch(url, { signal: AbortSignal.timeout(5000) });

How it is checked

• A one-line card in the prompt of a slice that touches matching files (dev_rules.slice_micro_rules).

How to silence it

A person can silence one finding with brevio-core: ignore R2.5 -- reason on the line or the line above. Without the reason it does not count. An agent cannot silence it: the agent hook and the MCP tools never honour the comment, and a pull request that adds one is reported until a reviewer allows it. Fixing the code is still the better answer.

To change what the rule flags, edit its definition in dev_rules.py or code_rules/__init__.py. That is a code change and is reviewed like one.

Related rules

• R2.6 Constant-time secret comparison
• R2.7 Secure cookie & CORS hygiene
• R2.8 No unsafe code or HTML sinks
• R2.1 Tenant context derivation
• Every rule