CVE-2026-9186

Langflow is vulnerable to stored cross-site scripting and IP spoofing due to unsanitized Markdown rendering and untrusted proxy header trust

Published Sep 4, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
Description
IBM Langflow OSS 1.0.0 through 1.11.2 allows remote authenticated attackers to bypass localhost-only MCP configuration installation by spoofing X-Forwarded-For: 127.0.0.1 header, enabling arbitrary writes to IDE config files (~/.cursor/mcp.json, etc.).

Remediation

Vendor Solution

IBM strongly recommends addressing the vulnerability now by upgrading Langflow OSS to version 1.11.3 https://pypi.org/project/langflow/

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Apple
Apple macos
Langflow
Langflow langflow
Linux
Linux linux Kernel
Microsoft
Microsoft windows
CPEs cpe:2.3:a:langflow:langflow:*:*:*:*:*:*:*:*
cpe:2.3:o:apple:macos:-:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows:-:*:*:*:*:*:*:*
Vendors & Products Apple
Apple macos
Langflow
Langflow langflow
Linux
Linux linux Kernel
Microsoft
Microsoft windows
Type Values Removed Values Added
Description IBM Langflow OSS 1.0.0 through 1.11.2 allows remote authenticated attackers to bypass localhost-only MCP configuration installation by spoofing X-Forwarded-For: 127.0.0.1 header, enabling arbitrary writes to IDE config files (~/.cursor/mcp.json, etc.).
Title Langflow is vulnerable to stored cross-site scripting and IP spoofing due to unsanitized Markdown rendering and untrusted proxy header trust
First Time appeared Ibm
Ibm langflow Oss
Weaknesses CWE-284
CPEs cpe:2.3:a:ibm:langflow_oss:1.0.0:*:*:*:*:*:*:*
cpe:2.3:a:ibm:langflow_oss:1.11.2:*:*:*:*:*:*:*
Vendors & Products Ibm
Ibm langflow Oss
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
ibm
Published
Updated
Sep 8, 2026, 4:48 PM
Reserved
May 21, 2026, 2:59 PM
Status
Analyzed
Published
Sep 4, 2026, 3:17 PM
Modified
Sep 8, 2026, 9:45 PM