CVE-2026-9077 Overview
CVE-2026-9077 affects IBM Langflow OSS versions 1.0.0 through 1.10.3. The vulnerability allows remote authenticated attackers to bypass localhost-only restrictions and write arbitrary Model Context Protocol (MCP) server configurations to Integrated Development Environment (IDE) configuration files on the host system. The flaw is categorized under [CWE-807]: Reliance on Untrusted Inputs in a Security Decision. Successful exploitation can compromise developer workstations by injecting attacker-controlled MCP endpoints into trusted IDE configurations.
Critical Impact
Authenticated attackers can write arbitrary MCP server entries into host IDE configuration files, pivoting from a Langflow instance to developer workstations and downstream AI tooling.
Affected Products
- IBM Langflow OSS 1.0.0
- IBM Langflow OSS versions 1.0.0 through 1.10.3
- Host systems running IDEs configured to consume MCP server entries written by Langflow
Discovery Timeline
- 2026-08-05 - CVE CVE-2026-9077 published to NVD
- 2026-08-05 - Last updated in NVD database
Technical Details for CVE-2026-9077
Vulnerability Analysis
IBM Langflow OSS enforces a localhost-only restriction intended to prevent remote clients from modifying host-resident configuration files. The restriction relies on request attributes that authenticated users can influence. An authenticated attacker submits crafted requests that satisfy the localhost check while originating from a remote session. Langflow then writes MCP server configuration entries into IDE configuration files on the host operating system.
The scope change reflected in the CVSS vector indicates the vulnerable component alters files owned by a separate trust boundary. Impact is weighted toward integrity because attackers control the contents of IDE configuration files. Those files are consumed by developer tools that automatically launch MCP servers, extending the blast radius beyond the Langflow process itself.
Root Cause
The root cause is reliance on untrusted inputs when deciding whether a request originates from localhost. Langflow accepts client-supplied signals as authoritative for the localhost determination rather than verifying the transport-layer source address at a trusted boundary. Authenticated remote callers can present values that satisfy the check and unlock privileged file-write behavior.
Attack Vector
Exploitation requires network access to a Langflow instance and valid low-privilege credentials. The attacker issues an API request that triggers MCP configuration writes while spoofing the signals used for the localhost check. Langflow serializes attacker-controlled MCP server definitions to IDE configuration files. When a developer next opens the IDE, the injected MCP server is loaded, giving the attacker a foothold in the developer environment and access to any data the IDE exposes to MCP servers.
No verified public proof-of-concept is available at publication time. Refer to the IBM Security Advisory for vendor-provided technical details.
Detection Methods for CVE-2026-9077
Indicators of Compromise
- Unexpected modifications to IDE configuration files that register MCP servers, particularly entries pointing to remote or unfamiliar endpoints.
- Langflow API requests to MCP configuration endpoints originating from non-loopback source addresses.
- New child processes launched by IDEs corresponding to MCP server executables that were not installed by the developer.
Detection Strategies
- Monitor file integrity on IDE configuration paths for MCP server additions or modifications outside of change windows.
- Correlate Langflow authentication events with subsequent file writes to host configuration directories.
- Alert on Langflow processes writing to user home directories or IDE configuration paths on shared hosts.
Monitoring Recommendations
- Enable verbose access logging on the Langflow API and forward logs to a centralized analytics pipeline.
- Baseline legitimate MCP server entries per developer workstation and alert on deviations.
- Track outbound connections initiated by IDE-spawned MCP server processes to identify attacker-controlled endpoints.
How to Mitigate CVE-2026-9077
Immediate Actions Required
- Upgrade IBM Langflow OSS to a fixed release beyond 1.10.3 as directed in the IBM Security Advisory.
- Restrict network exposure of Langflow instances to trusted management networks and require strong authentication.
- Audit IDE configuration files on hosts that have run affected Langflow versions and remove unauthorized MCP entries.
Patch Information
IBM has published remediation guidance in the IBM Security Advisory. Apply the vendor-provided fixed version to eliminate the localhost bypass. Confirm the upgrade on every Langflow node, including development and staging instances, before restoring network access.
Workarounds
- Bind Langflow to loopback interfaces only and place authenticated remote access behind a reverse proxy that enforces source-IP allow-lists.
- Revoke unnecessary Langflow user accounts and rotate credentials for any account that could reach affected endpoints.
- Run Langflow under a service account without write permissions to developer home directories or IDE configuration paths.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
