Langflow: IDOR/BOLA in Monitor API — Missing Ownership Enforcement on 7 Endpoints

published 2026-06-16 4 mo ago modified 2026-10-26 13 d ago also EUVD-2026-38519 , GHSA-9c59-2mvc-vfr8 , PYSEC-2026-242

cvss: 8.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits: 0; none known

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.0, Langflow's /api/v1/monitor router exposes 7 endpoints that perform read, write, and delete operations on user-owned resources — messages, sessions, build artifacts, and LLM transaction logs — without verifying that the authenticated requester owns the targeted resource. Any authenticated user can read, modify, rename, or permanently delete another user's data by supplying the target's resource ID or flow_id. This is a classic IDOR/BOLA vulnerability. Notably, the same source file (monitor.py) contains one correctly-implemented endpoint that uses an ownership check, demonstrating the correct pattern was known but inconsistently applied. This vulnerability is fixed in 1.9.0.

Patch / fix

fixed in 3

pypi langflow 1.9.0
langflow langflow 1.9.0
langflow-ai langflow 1.9.0

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: total
Assessed: 4 mo ago (2026-06-24)

Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/langflow-ai/langflow/security/advisories/GHSA-9c59-2mvc-vfr8 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
GitHub	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
OSV	3.1	8.8	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem	package	affected	fixed in
pypi	langflow	<1.9.0	1.9.0

Affected products

langflow-ai langflow

Classification

Weakness

CWE-639 Authorization Bypass Through User-Controlled Key

References

github.com /langflow-ai/langflow/security/advisories/GHSA-9c59-2mvc-vfr8
web, exploit, vendor-advisory, evidence
nvd.nist.gov /vuln/detail/CVE-2026-33760
advisory
github.com /langflow-ai/langflow
package
github.com /pypa/advisory-database/tree/main/vulns/langflow/PYSEC-2026-242.yaml
web

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary