Crawl4AI: Unauthenticated RCE via Chromium launch-argument injection in browser_config.extra_args
- When
- Where
- Global (internet)
- Category
- cyber_advisory · pip
### Summary The Docker API server accepted a request-supplied `browser_config.extra_args`, which flowed into Chromium's launch arguments. An attacker could inject Chromium switches that replace a child-process launch command (`--utility-cmd-prefix`, `--renderer-cmd-prefix`, `--gpu-launcher`, `--browser-subprocess-path`) together with `--no-zygote`, causing Chromium to fork/exec an attacker-controlled command as the container's runtime user. The Docker API is unauthenticated by default, so a single request yields arbitrary command execution. The earlier `extra_args` SSRF patch (0.8.9) used a denylist scoped to proxy/DNS flags; a denylist of launch switches is inherently incomplete, and these command-execution switches were not covered. ### Affected paths `/crawl`, `/crawl/stream`, `/crawl/job` accepting a request `browser_config.extra_args`. ### Impact Unauthenticated remote code execution as the container runtime user; full read/write of application data, mounted secrets, environment, and tokens, and out-of-band exfiltration independent of the HTTP response. ### Fix 0.9.0 establishes a trust boundary for request-supplied configuration: `extra_args` (along with other power fields such as `proxy`, `user_data_dir`, `cdp_url`, `init_scripts`) is a forbidden field for untrusted request bodies. Any request that sets `extra_args` is rejected with HTTP 400 rather than scrubbed against an always-incomplete denylist. In-process SDK callers (trusted) are unaffected. ### Workarounds - Upgrade to the patched version (0.9.0). - Enable authentication (`CRAWL4AI_API_TOKEN`) and restrict who can reach the API. - Run the container with a restrictive seccomp profile and no ability to exec helper binaries. ### Credits Y4tacker - reported the `--no-zygote` + `--utility-cmd-prefix` command-injection chain with a confirmed in-container PoC and an allowlist/reject recommendation. UDU_RisePho (hoanggxyuuki) - independently reported the request-supplied Chromium launch-flag RCE class (`--renderer-cmd-prefix`), confirmed still reproducing on 0.8.9.
Sources
- GitHub Advisory Database ↗ · first seen 2026-06-18 17:25 UTC
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