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GHSA-2jq4-q6vv-4cp3

CriticalCVSS 9.6 / 10
Published Jun 18, 2026·Last modified Jun 18, 2026
Affected Components(0)

No affected components available

Description

Summary

When the crawler saves a downloaded file, the destination filename was taken from attacker-influenced input and joined to the downloads directory with no confinement. A filename containing an absolute path (e.g. /etc/cron.d/evil) or ../ traversal escaped the downloads directory, giving an arbitrary file write with attacker-controlled contents. Because the written bytes are attacker-controlled, this escalates to remote code execution (overwriting a shell rc-file, ~/.ssh/authorized_keys, a cron entry, or a Python module on the import path).

Affected paths

Two download sinks in crawl4ai/async_crawler_strategy.py:

  • HTTP crawler (AsyncHTTPCrawlerStrategy): the filename is parsed from the response Content-Disposition header by _extract_filename() and written via aiofiles.open(filepath, 'wb'). Reachable directly via the SDK, and via the unauthenticated Docker /crawl endpoint when an HTTPCrawlerConfig is supplied.
  • Browser crawler (AsyncPlaywrightCrawlerStrategy): the download's suggested_filename (controllable by the visited page) is joined to downloads_path and written via download.save_as().

The HTTP-strategy sink is reachable pre-auth on the default Docker deployment; both are reachable for SDK users simply by crawling an attacker-controlled URL. The default Playwright crawl path that does not trigger a download is unaffected.

Impact

Arbitrary file write with attacker-controlled content as the user running the crawler, escalating to remote code execution.

Fix

Both sinks now resolve the destination through a single hardened helper (_safe_download_filepath) that reduces the attacker-influenced name to a bare basename (dropping absolute paths and .. components) and re-checks, via realpath, that the resolved path stays inside the downloads root (defeating symlink/TOCTOU escapes). A traversal attempt is rejected; normal downloads are unchanged.

Workarounds

  • Upgrade to the patched version (0.9.0).
  • Run the crawler as an unprivileged user with a dedicated, isolated downloads directory on a volume with no sensitive paths writable.
  • Enable authentication (CRAWL4AI_API_TOKEN) on the Docker server.

Credits

Y4tacker - reported the Content-Disposition path traversal in the HTTP crawler with a clear PoC and a basename + realpath-containment fix recommendation.

Risk Scores
Base Score
9.6

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.

Threat Intelligence
8.8

Exploitation activity has been observed. Apply available patches or mitigations urgently.

EPSS
0.60%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Critical severity
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