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PYSEC-2026-377
No affected components available
Summary
Langflow is vulnerable to Path Traversal in the Knowledge Bases API (DELETE /api/v1/knowledge_bases). This occurs because user-supplied knowledge base names are concatenated directly into file paths without proper sanitization or boundary validation. An authenticated attacker can exploit this flaw to delete arbitrary directories anywhere on the server's filesystem, leading to data loss and potential service disruption.
Details
The vulnerability exists in the delete_knowledge_bases_bulk function within src/backend/base/langflow/api/v1/knowledge_bases.py.
This function constructs file paths directly from the user-supplied kb_names parameter. While other knowledge base endpoints safely route through standard path resolution (e.g., _resolve_kb_path()), the bulk delete handler bypasses this entirely. It builds the path manually and passes it directly to shutil.rmtree() without validating if the resulting path resolves outside the intended user directory.
PoC (Proof of Concept)
For the Bulk Delete endpoint, an authenticated attacker can supply a traversal sequence in the kb_names parameter:
../victim_user/kb_name
Because the path is passed directly to shutil.rmtree() without containment checks, this payload deletes directories outside the intended scope.
Impact
Any Langflow instance exposing this endpoint to authenticated users is vulnerable. This exposes the server to:
- Cross-user data compromise: Deletion of directories within another tenant's knowledge base space.
- Arbitrary filesystem manipulation: Directory deletion at any path on the server where the application has write permissions.
- Service disruption & Data Loss: Deletion of critical application files or unrecoverable data loss if backups are co-located on the same filesystem.
Fixes
The issue was addressed in PR #12243, which applies Path.resolve() to normalize the supplied path and validates that it starts with the authenticated user's directory before deletion. Subsequent updates (backported from PR #12337) introduced robust containment checks using Path.is_relative_to() to prevent prefix-ambiguity bugs.
Acknowledgements
Thanks to the security researchers who responsibly disclosed this vulnerability:
- @ddlxstudio
- @nekros1xx
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The vulnerability can affect other systems as well, not just the initial system. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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