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CVE-2026-55255 CISA KEV high CVSS 8.4

[KEV] Vulnerability in Langflow (CVE-2026-55255)

Summary

Vulnerability in Langflow (CVE-2026-55255). Confidential information can be exposed externally. Exploitable via get_flow_by_id_or_endpoint_name. Listed in CISA KEV — actively exploited. Mitigation: upgrade to 1.9.1 or later.

Original description

The description as published by the source.

Summary

Insecure Direct Object Reference (IDOR) vulnerability in /api/v1/responses endpoint allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request.

Details

The vulnerability exists in the get_flow_by_id_or_endpoint_name helper function in src/backend/base/langflow/helpers/flow.py (lines 399-414).

When a flow is accessed via UUID (flow_id), the function queries the database directly without verifying if the authenticated user owns that flow:

# src/backend/base/langflow/helpers/flow.py:399-414
async def get_flow_by_id_or_endpoint_name(flow_id_or_name: str, user_id: str | UUID | None = None) -> FlowRead:
    async with session_scope() as session:
        try:
            flow_id = UUID(flow_id_or_name)
            # When using UUID, query directly WITHOUT checking user_id
            flow = await session.get(Flow, flow_id)  # ❌ No user_id check!
        except ValueError:
            endpoint_name = flow_id_or_name
            stmt = select(Flow).where(Flow.endpoint_name == endpoint_name)
            # Only when using endpoint_name is user_id checked
            if user_id:
                stmt = stmt.where(Flow.user_id == uuid_user_id)

This function is used by the /api/v1/responses endpoint (defined in [src/backend/base/langflow/api/v1/openai_responses.py:589…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory CISA KEV

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-2026-55255 has been found in Langflow.
Attackers can target a specific entry point like get_flow_by_id_or_endpoint_name over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.4/10.
Note: CISA has officially confirmed this is actively exploited in the wild. Treat it with elevated urgency.
What to do: upgrade Langflow to 1.9.1 or later.
If unsure, ask your IT team or search "Langflow CVE-2026-55255" on the vendor's site.

CVE-2026-55255 (Langflow) — CWE-639 / CVSS v3 8.4
Attack vector: remote (network-reachable) / no user interaction
Attack surface: get_flow_by_id_or_endpoint_name / user_id / endpoint_name
Patched: 1.9.1 — apply immediately
Listed in CISA KEV — actively exploited, treat as top priority.
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.

❓ What is the problem

A vulnerability (CWE-639) exists in Langflow. Attackers reach the vulnerable code path via get_flow_by_id_or_endpoint_name.

📍 Affected scope

Check the vendor advisory for the affected versions of Langflow. Attack surface: get_flow_by_id_or_endpoint_name / user_id / endpoint_name.

🔥 Severity

Severity: High (CVSS 8.4/10). Confidential information can be exposed externally. Listed in CISA KEV — actively exploited in the wild, treat as top priority.

🔧 How to fix

Update to 1.9.1.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. 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

  1. 1
    Identify 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。

  2. 2
    Consider incident declaration escalate 
    Notify SOC / on-call

    CISA KEV登録済 = 実環境で悪用が観測されている。侵入の兆候があればインシデント対応宣言、無くてもパッチ適用までWAF強化を最優先で。

  3. 3
    Apply patch patch 
    Upgrade Langflow to 1.9.1

    ステージング環境で 1.9.1 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を含めること。

  4. 4
    Post-deployment verification verify 
    Confirm patched version is live in production

    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。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

pip langflow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.9.1"}]}]
PyPI langflow
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.9.1"}]}]

References

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