Security Bulletin
Summary
Langflow OSS contains unauthenticated access vulnerability in /api/v1/build_public_tmp/ router endpoints allowing arbitrary job_id access without authentication or authorization checks. Two endpoints affected: (1) GET /build_public_tmp/{job_id}/events (chat.py:758) streams live build events for any flow including PRIVATE flows belonging to any user, exposing customer prompts, LLM responses, API keys, internal documents from RAG pipelines, and server-side Python tracebacks revealing filesystem layout; (2) POST /build_public_tmp/{job_id}/cancel (chat.py:780) cancels any in-flight flow build enabling repeatable denial-of-service against chosen tenants. Both endpoints lack Depends(get_current_active_user), flow_id lookup, and access_type checks. Downstream helpers get_flow_events_response and cancel_flow_build accept only (job_id, queue_service) without compensating authorization. Proof of concept: victim creates PRIVATE flow (flow_id be17f527-0f9b-4289-b0e0-018cd1aa87a0) with embedded sentinel CUSTOMER_PII_MY6PRQ2L3E, starts authenticated build capturing job_id 88c6f1c7-58ed-4524-a7d0-6eab0eea6f29; attacker performs unauthenticated GET to /build_public_tmp/{job_id}/events receiving HTTP 200 with 4794 bytes including session_id matching private flow UUID, full Python traceback exposing internal paths, and session metadata; attacker performs unauthenticated POST to /build_public_tmp/{job_id}/cancel receiving success:true. Negative control with invalid job_id returns HTTP 404 proving 200 responses came from real private-flow builds.
Vulnerability Details
CVEID: CVE-2026-10560
DESCRIPTION: Langflow OSS contains a missing authentication vulnerability in /api/v1/build_public_tmp/ endpoints that allows an unauthenticated attacker to read build event data or cancel jobs using a valid job identifier, resulting in information disclosure and denial of service.
CWE: CWE-287: Improper Authentication
CVSS Source: IBM
CVSS Base score: 8.2
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| Langflow OSS | 1.0.0-1.9.6 |
Remediation/Fixes
IBM strongly recommends addressing the vulnerability now by upgrading Langflow OSS to version 1.10.0
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
25 Jun 2026: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
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Document Information
Modified date:
25 June 2026
Initial Publish date:
25 June 2026
UID
ibm17277996