CVE-2026-8505: Langflow: Unauthenticated Flow Execution via Webhook Authentication Bypass

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.7%, percentile 53: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 53% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes langflow (PyPI) >= 1.7.0, <= 1.9.0, fixed in 1.9.1. Check your lockfile, including transitive dependencies.

What it is

IBM Langflow OSS 1.0.0 through 1.10.0 has a vulnerability in Langflow's webhook authentication logic allows unauthenticated users to trigger the execution of any flow. The system incorrectly bypasses API key validation when the WEBHOOKAUTHENABLE configuration is set to False (which is the default setting). This allows a remote attacker who knows a flow's UUID to execute it as if they were the owner, potentially leading to Remote Code Execution (RCE).

From the GitHub advisory

Summary A vulnerability in Langflow's webhook authentication logic allows unauthenticated users to trigger the execution of any flow. The system incorrectly bypasses API key validation when the WEBHOOKAUTHENABLE configuration is set to False. This allows a remote attacker who knows a flow's UUID to execute it as if they were the owner, potentially leading to Remote Code Execution (RCE) or Denial of Service (DoS).

Details The WEBHOOKAUTHENABLE setting was introduced in v1.7.0 (#9139) with a default of False. The root cause is in the webhook authentication path, AuthService.getwebhookuser (src/backend/base/langflow/services/auth/service.py; the thin wrapper in src/backend/base/langflow/services/auth/utils.py just delegates to it):

By default (v1.7.0 through v1.9.0), Langflow treats WEBHOOKAUTHENABLE as False, meaning all webhook endpoints are public. This relies exclusively on the secrecy of the flowid (UUID), which is an insecure practice (Security by Obscurity).

A related report, GHSA-6g4m-v5q2-475v, demonstrated a concrete RCE chain through this same bypass using the PythonCodeStructuredTool component (exec() on flow-authored Python code). That report is a duplicate of this root cause and has been closed in favor of this advisory; credit for that PoC has been added here.

PoC 1. Identify a valid flowid for a flow that performs a sensitive action (e.g., sending an email, writing to a database, or executing a Python script). 2. Execute a POST request to the webhook endpoint without any Authorization header or API Key:

Weakness type: CWE-306.

Product: langflow (PyPI) · Assigned by: ibm · Published: 2026-07-17

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.72% probability of exploitation activity in the next 30 days; percentile 53.

Timeline

• 2026-07-17 — CVE record published by ibm
• 2026-07-23 — CVE record last updated
• 2026-10-05 — GitHub-reviewed advisory GHSA-cf6m-vc3m-7cgm published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. ibm.com ibm.com

Vulnerability records

1. GitHub Advisory GHSA-cf6m-vc3m-7cgm github.com
2. CVE.org record CVE-2026-8505 cve.org
3. NVD entry CVE-2026-8505 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com

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