dbcve.org
Crawl4aiApplication · Kidocode

CVE-2026-53753

CRITICAL · 10.0 CVSS v3.1 Published 2026-06-23
Fix available
A fix is available. Upgrade to 0.8.7 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Crawl4AI is an open-source LLM friendly web crawler & scraper. Prior to 0.8.7, the _safe_eval_expression() function in the computed fields feature uses an AST validator that only blocks attributes starting with underscore. Python generator and frame object attributes (gi_frame, f_back, f_builtins) do NOT start with underscore, enabling a complete sandbox escape to achieve arbitrary code execution. The attack requires no authentication (JWT disabled by default) and is triggered via POST /crawl with a crafted extraction schema. This vulnerability is fixed in 0.8.7.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The _safe_eval_expression() function in Crawl4AI's computed fields feature uses an AST validator that only blocks attributes starting with an underscore. However, Python generator attributes (gi_frame) and frame object attributes (f_back, f_builtins) do not start with underscore, allowing a complete sandbox escape and arbitrary code execution. The attack is unauthenticated and triggered via POST /crawl with a crafted extraction schema.

MitigationUpgrade to Crawl4AI version 0.8.7 or later, which contains the fix for this sandbox escape vulnerability.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Crawl4aiApplication
Affected:< 0.8.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Crawl4AI version
    Run `pip show crawl4ai` or check the installed package version using your package manager. Compare against the affected range: versions before 0.8.7 are vulnerable.
    Affected if Installed version is lower than 0.8.7
  2. Verify computed fields feature is accessible
    Confirm that the /crawl endpoint accepts POST requests with an extraction_schema or computed_fields parameter in the request body.
    Affected if The extraction schema feature is enabled and accessible via the web API
  3. Inspect AST validator configuration
    Examine the _safe_eval_expression() function in the Crawl4AI source code. Look for the AST validator logic that blocks attributes starting with underscore but allows gi_frame, f_back, or f_builtins.
    Affected if The AST validator only checks for underscore-prefixed attributes and does not block generator/frame object attributes
  4. Check API exposure
    Confirm the /crawl endpoint is exposed without authentication. This is the unauthenticated attack vector.
    Affected if The API endpoint does not require authentication

A user is affected if running Crawl4AI version below 0.8.7 AND the computed fields/extraction schema feature is accessible (especially without authentication).

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.8.7 or later
Fixed in 0.8.7
Interim mitigation

Upgrade to Crawl4AI version 0.8.7 or later, which contains the fix for this sandbox escape vulnerability.

Recommended fix High confidence

0.8.7

  1. 1. Identify the current Crawl4ai installation method (pip, docker, or source)
  2. 2. For pip installation: Run 'pip install crawl4ai==0.8.7' to upgrade to the fixed version
  3. 3. For docker: Pull the updated image with the tag corresponding to version 0.8.7
  4. 4. If installed from source: Navigate to the project directory and run 'git pull' then checkout tag v0.8.7 or ensure the version is updated to 0.8.7
  5. 5. Restart any running Crawl4ai services to load the patched version
  6. 6. Verify the upgrade was successful by checking the installed version (e.g., 'pip show crawl4ai' or via API endpoint)

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Crawl4ai Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-53753 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data