Description

PraisonAI: Crawl4AI/Chromium backend is also affected by the web_crawl SSRF validation bypass

Summary

The DNS-rebinding / redirect SSRF bypass in PRAI-05 is not limited to the httpx/urllib backend. When crawl4ai (headless Chromium via Playwright) is installed, web_crawl auto-selects provider=crawl4ai, and the headless browser re-resolves DNS and follows redirects on its own — with no per-connection SSRF guard. Runtime-confirmed read-back of the internal canary via both DNS rebinding and redirect (provider: "crawl4ai"). Status: runtime-confirmed addendum to PRAI-05.

Details

Affected component

Package praisonaiagents 4.6.63. Backend selected when crawl4ai+Playwright are installed.

Files: src/praisonai-agents/praisonaiagents/tools/web_crawl_tools.py (_crawl_with_crawl4ai) and src/praisonai-agents/praisonaiagents/tools/crawl4ai_tools.py (standalone crawl wrappers).

Vulnerable code / root cause

Path: src/praisonai-agents/praisonaiagents/tools/web_crawl_tools.py

Function: _crawl_with_crawl4ai

Snippet:

async with AsyncWebCrawler() as crawler:
    for url in urls:
        result = await crawler.arun(url=url)   # headless browser: re-resolves DNS, follows redirects

Path: src/praisonai-agents/praisonaiagents/tools/crawl4ai_tools.py

Function: Crawl4AITools.crawl / crawl4ai

Snippet:

result = await crawler.arun(url=url, config=config)   # no _is_safe_crawl_url / no per-connect validation

Issue: the only SSRF check is the single pre-fetch _is_safe_crawl_url() on the initial URL string in web_crawl() (see PRAI-05). The headless browser then resolves and connects independently and follows redirects in-browser — no resolved-IP pinning, no per-hop/per-connect validation. Input (urls) is attacker/agent-controlled; the sink is crawler.arun(url=...); the guard is bypassed by DNS rebinding (TOCTOU) and by redirects (followed in-browser).

Attack flow / Why bypassed / Security boundary

Identical to PRAI-05: TOCTOU between the guard's resolution and the browser's connection; redirects followed in-browser; internal response returned as crawl content. See PRAI-05.

Proof of Concept

Environment

crawl4ai + Playwright Chromium installed in a dedicated runtime container (127.0.0.1:18081), same controlled internal canary + rebinding DNS. Runnable assets: PraisonAI-Runtime-Repro\runtime-files\ (docker-compose.crawl.yml).

Steps to reproduce

SSRF-04-01-Crawl4AI-DNS-Rebind-Trigger → 127.0.0.1:18081:

POST /tool/web_crawl HTTP/1.1
Host: 127.0.0.1:18081
Content-Type: application/json

{"url":"http://rebind.lab:8081/secret"}

Redirect variant SSRF-04-03-Crawl4AI-Redirect-Readback: {"url":"http://redirector:8082/redirect-to-internal"}.

Expected result

The crawl backend refuses internal destinations regardless of DNS timing/redirects.

Actual result

HTTP 200, "provider":"crawl4ai", response content contains PRAISONAI_INTERNAL_SECRET_CANARY_7f3a91 + FAKE_INTERNAL_TOKEN_DO_NOT_USE_7f3a91 for both the DNS-rebinding and the redirect payload.

Screenshots

Crawl4AI DNS rebinding read-back

The attacker-controlled rebind.lab URL is accepted by the Crawl4AI-backed web_crawl endpoint. PraisonAI returns the internal canary response body containing PRAISONAI_INTERNAL_SECRET_CANARY_7f3a91.

Crawl4AI DNS rebinding runtime evidence

The runtime log shows the Crawl4AI/Chromium backend resolving rebind.lab to an internal Docker IP during the fetch phase. The internal canary receives GET /secret from a headless Chrome user agent.

Crawl4AI redirect read-back

The attacker-controlled redirector URL is accepted by the Crawl4AI-backed endpoint. PraisonAI follows the redirect and returns the internal canary response body.

Crawl4AI redirect runtime evidence

The controlled redirector returns 302 -> http://internal-canary:8081/secret, and the internal canary receives GET /secret from the Crawl4AI/Chromium backend.

Impact

Same class as PRAI-05: read-back SSRF to internal/metadata services, now on the crawl4ai backend. Broadens the affected surface (the flaw is in the shared validate-without-pinning design, not one backend).

Suggested remediation

Resolve-once + IP-pin + per-connect validation must also cover the crawl4ai backend (constrain the headless browser to the validated IP, or allowlist crawl destinations).

Mitigation

Aliases

References