Vulnerability in langflow (CVE-2026-55446)
Summary
Vulnerability in langflow (CVE-2026-55446). Risk of unauthorized operations or information disclosure. Exploitable via POST /api/v1/files/upload/test. Mitigation: upgrade to 1.0.19 or later.
Original description
The description as published by the source.
Summary
An attacker can send a /api/v1/files/upload/ request without any authentication token/cookies and abuse a very long multipart form boundary to make the langflow app unusable for all users for an indefinite amount of time.
Details
https://github.com/langflow-ai/langflow/blob/v1.0.18/src/backend/base/langflow/api/v1/files.py#L40
The file upload function will try to process the multipart form data even if it is malformed and contains a payload such as an extremely large amount of hyphens after the boundary. It also does not do the authentication check before trying to process this data so an unauthenticated attacker can perform this as well as authenticated users.
Additionally, an attacker doesn't even need to know a valid UUID of a flow to send this request because the server will still try to process the large boundary even with any random value in place of the flow ID.
PoC
An attacker makes this request to upload a file without valid authentication information or a valid flow ID:
POST /api/v1/files/upload/test HTTP/1.1
Host: 127.0.0.1:7860
Content-Length: 3000192
Accept-Language: en-US,en;q=0.9
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.6613.120 Safari/537.36
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryorGBAKSkv5wR6WqJ
Accept: application/json, text/plain, */*
Origin: http://127.0.0.1:7860
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
------Web…
Source: GitHub Security Advisories (Global) 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-2026-55446 has been found in langflow.
Attackers can target a specific entry point like POST /api/v1/files/upload/test over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade langflow to 1.0.19 or later.
If unsure, ask your IT team or search "langflow CVE-2026-55446" on the vendor's site.
CVE-2026-55446 (langflow) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: POST /api/v1/files/upload/test / check_boundary / get_current_active_user
Patched: 1.0.19 — 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-400) exists in langflow. Attackers reach the vulnerable code path via POST /api/v1/files/upload/test without authentication.
Check the vendor advisory for the affected versions of langflow. Attack surface: POST /api/v1/files/upload/test / check_boundary / get_current_active_user.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.0.19.
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 /api/v1/files/upload/test requests with malformed payloads or SQL meta-characters. Run grep -r 'langflow' . 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 'langflow' . | 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
langflow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 /api/v1/files/upload/test' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /api/v1/files/upload/test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 langflow to 1.0.19ステージング環境で 1.0.19 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 /api/v1/files/upload/test 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 github.com
- web github.com
- web github.com