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CVE-2026-18904 – Sensitive Information Disclosure / Message Injection – Langflow OSS 1.0.0–1.11.1

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Summary

CVE-2026-18904 is an authorization bypass vulnerability (CWE-639, Authorization Bypass Through User-Controlled Key) affecting IBM Langflow OSS versions 1.0.0 through 1.11.1. A namespace collision between user identifiers in flow metadata allows a remote, unauthenticated attacker to read another user’s public-playground chat history and inject unauthorized messages into it. The flaw carries a CVSS v3.1 base score of 8.2 (High).

Technical details

  • Root cause: Flow metadata exposes owner user IDs, and a namespace collision between user identifiers allows one user’s identifier to be conflated with another’s within the public-playground chat mechanism.
  • Trigger conditions: An attacker interacts with a Langflow public-playground chat associated with a flow whose metadata leaks the owning user’s identifier.
  • Attack vector: Network-based, requires no authentication and no user interaction (AV:N/AC:L/PR:N/UI:N).
  • Impact: High confidentiality impact (attacker can read another user’s private chat history) and low integrity impact (attacker can inject unauthorized messages into that chat history); no availability impact.

Affected software

  • IBM Langflow OSS versions 1.0.0 through 1.11.1

Severity

  • CVSS v3.1 Base Score: 8.2 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Mitigation and recommended actions

  • Immediate: Upgrade Langflow OSS to version 1.11.2 or later, available via PyPI.
  • If immediate patching is not possible: No vendor-documented workaround exists for this issue; restrict network exposure of Langflow instances (particularly public-playground endpoints) until the upgrade can be applied, and review chat history logs for signs of unauthorized access.

References

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