Vulnerability in crawl4ai (CVE-2026-56258)
Summary
Vulnerability in crawl4ai (CVE-2026-56258). Successful exploitation can lead to full system takeover. Exploitable via POST /screenshot. Mitigation: upgrade to 0.8.8 or later.
Original description
The description as published by the source.
Summary
Three backward-compatible hardening fixes in the Docker API server. The headline issue is an arbitrary file write via the screenshot/PDF output_path.
1. Arbitrary file write via output_path symlink / TOCTOU (primary)
POST /screenshot and POST /pdf accept an output_path constrained to ALLOWED_OUTPUT_DIR by validate_output_path. The 0.8.7 check was string-only: it did not resolve symlinks, so a symlinked path component inside the output directory could redirect the write outside the directory, and the final open() followed symlinks. On a deployment where the runtime user can write executable/cron locations this is an arbitrary-write to code-execution primitive. The API is unauthenticated by default.
Fix: validate_output_path now resolves the real path (symlinks) of the parent and re-checks containment, and the write uses O_NOFOLLOW (write_output_file). output_path remains supported.
2. CRLF log injection (CWE-117)
User-controlled URLs/errors reflected into log lines could embed CR/LF and forge additional log entries. Fix: a logging filter strips CR/LF/control characters from all records.
3. Webhook request-header injection (CWE-93/CWE-113)
User-supplied webhook headers were sent verbatim, allowing CRLF and hop-by-hop / sensitive header injection on the outbound webhook request. Fix: webhook headers are validated (name pattern, no control characters, deny Host/Content-Length/Transfer-Encoding/Authorization/Cookie/..…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-56258 has been found in crawl4ai.
Attackers can target a specific entry point like POST /screenshot over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.1/10.
What to do: upgrade crawl4ai to 0.8.8 or later.
If unsure, ask your IT team or search "crawl4ai CVE-2026-56258" on the vendor's site.
CVE-2026-56258 (crawl4ai) — CWE-117 / CVSS v3 8.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: POST /screenshot / POST /pdf / output_path / ALLOWED_OUTPUT_DIR
Patched: 0.8.8 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-117) exists in crawl4ai. Attackers reach the vulnerable code path via POST /screenshot without authentication.
Check the vendor advisory for the affected versions of crawl4ai. Attack surface: POST /screenshot / POST /pdf / output_path / ALLOWED_OUTPUT_DIR.
Severity: High (CVSS 8.1/10). Successful exploitation can lead to full system takeover.
Update to 0.8.8.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /screenshot requests with malformed payloads or SQL meta-characters. Run grep -r 'crawl4ai' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'crawl4ai' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
crawl4aiを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'POST /screenshot' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /screenshotへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade crawl4ai to 0.8.8ステージング環境で 0.8.8 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against POST /screenshot on staging to confirm patch closes the vectorパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番では Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
References
- package github.com
- web github.com
- web vulncheck.com
- web nvd.nist.gov
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com