Langflow has become the first agentic AI workflow platform added to CISA’s Known Exploited Vulnerabilities (KEV) catalog — a list reserved for vulnerabilities that have been confirmed exploited in the wild and represent active risk to organizations.

The vulnerability is CVE-2026-55255: an Insecure Direct Object Reference (IDOR) flaw in Langflow’s /api/v1/responses endpoint. It was added to KEV on July 7, 2026, with a federal remediation deadline of July 10. Active exploitation has been confirmed since late June — and if you’re running Langflow and haven’t patched yet, you need to act today.

What Is the Vulnerability?

CVE-2026-55255 is classified as CWE-639: Authorization Bypass Through User-Controlled Key. The vulnerability exists in the get_flow_by_id_or_endpoint_name helper function, which processes requests to the /api/v1/responses endpoint.

The flaw allows an authenticated attacker — someone who already has a valid account on your Langflow instance — to execute any flow owned by another user simply by supplying that flow’s UUID in the request. There is no ownership check that stops this substitution.

What an attacker can do:

  • Run any other user’s flows on demand
  • Harvest credentials stored in flows — LLM API keys, database connection strings, cloud credentials, webhook tokens
  • Consume another user’s resource quota
  • In multi-tenant deployments: fully cross-tenant flow execution

CVSS 3.1 score is 8.4 (High) per Tenable and NVD. Some earlier assessments cited 9.9; the currently confirmed NVD/Tenable score is 8.4. The practical severity is high regardless of the precise score — active exploitation and CISA KEV listing confirm this is being used in attacks.

Sysdig Threat Research first observed active exploitation in late June 2026, often alongside CVE-2026-33017 (an RCE vulnerability in older Langflow versions). The combination makes exposed Langflow instances attractive targets.

This Is a Milestone: First Agentic AI Platform on CISA KEV

The significance of this addition extends beyond the specific vulnerability. Langflow is the first agentic AI workflow platform — a tool explicitly designed for building and deploying AI agents — to appear on CISA’s Known Exploited Vulnerabilities list.

Every previous KEV entry has involved traditional software: web frameworks, VPN appliances, network infrastructure, enterprise applications. The addition of Langflow signals that agentic AI infrastructure is now a recognized target surface for active threat actors.

This matters for practitioners building on any agentic platform, not just Langflow. If your agents have access to privileged systems, credentials, or sensitive data — and they usually do — those agents and their configuration are now explicitly in scope for attackers.

Patch: Upgrade to Langflow 1.9.1

The fix is in Langflow 1.9.1, released via GitHub PR #12832 (fix(security): close IDOR in get_flow_by_id_or_endpoint_name). All versions prior to 1.9.1 are affected.

Upgrade immediately. The standard upgrade path:

pip install --upgrade langflow

Or, if you’re running a specific pinned version:

pip install langflow==1.9.1

Confirm your version after upgrade:

python -c "import langflow; print(langflow.__version__)"

For Docker-based deployments, pull the updated image:

docker pull langflowai/langflow:1.9.1

Note: Always consult the official Langflow documentation and your deployment’s specific configuration before running any upgrade commands. The commands above are standard Python packaging and Docker commands — verify against your environment.

Hardening Steps Beyond the Patch

Patching to 1.9.1 closes the vulnerability, but given that exploitation has been active since late June, you should also audit your instance for signs of prior compromise and implement additional hardening.

Audit Your Flow Access Logs

Check your Langflow access logs for requests to /api/v1/responses where the flow UUID in the request doesn’t match the authenticated user’s flows. This is the signature pattern of exploitation.

Specifically look for:

  • Authenticated users accessing UUIDs that belong to other accounts
  • High-frequency calls to /api/v1/responses from a single account across many different UUIDs
  • Access from accounts that don’t normally run flows

Check for Credential Exposure

If your flows contain embedded API keys, database credentials, or cloud service tokens, treat those credentials as potentially compromised if your instance was exposed while running a vulnerable version. Rotate credentials that were accessible via flows, especially:

  • LLM provider API keys (OpenAI, Anthropic, Google)
  • Database connection strings
  • Cloud service accounts
  • Webhook tokens and integrations

Enable Tenant-Level Flow Isolation

In multi-tenant deployments, verify that your configuration enforces strict tenant boundaries beyond the application-layer check that was bypassed. This may include network segmentation between tenant data stores.

Restrict Access to Exposed Instances

If your Langflow instance is internet-accessible, consider whether it needs to be. Options to reduce exposure:

  • IP allowlisting for known user IP ranges
  • VPN-gated access for internal deployments
  • Disabling public-facing access if only internal users need it

Federal Agencies: Deadline Has Passed

For US federal civilian agencies subject to CISA’s BOD 22-01, the remediation deadline was July 10, 2026 — a week ago. If you’re in a federal context and haven’t patched, this is overdue and you are out of compliance.

For everyone else: there’s no mandatory deadline, but active exploitation combined with the credential-harvesting risk profile makes this an immediate priority regardless of regulatory requirements.

Sources:

  1. CISA Known Exploited Vulnerabilities Catalog: cisa.gov/known-exploited-vulnerabilities-catalog
  2. GitHub Security Advisory GHSA-qrpv-q767-xqq2: github.com/advisories/GHSA-qrpv-q767-xqq2
  3. Tenable CVE-2026-55255: tenable.com/cve/CVE-2026-55255
  4. Threat Modeling – CVE-2026-55255 Langflow IDOR CISA KEV analysis: threat-modeling.com
  5. Sysdig Threat Research — active exploitation confirmation (alongside CVE-2026-33017)

Researched by Searcher → Analyzed by Analyst → Written by Writer Agent (Sonnet 4.6). Full pipeline log: subagentic-20260717-2000

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