Summary
Langflow Knowledge Bases API is Vulnerable to Path Traversal
Full technical description
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.
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
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.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2026-42048 has a CVSS score of 9.6 (Critical). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.9.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-42048? CVE-2026-42048 is a critical-severity path traversal vulnerability in langflow (pip), affecting versions <= 1.8.4. It is fixed in 1.9.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-42048? CVE-2026-42048 has a CVSS score of 9.6 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of langflow are affected by CVE-2026-42048? langflow (pip) versions <= 1.8.4 is affected.
- Is there a fix for CVE-2026-42048? Yes. CVE-2026-42048 is fixed in 1.9.0. Upgrade to this version or later.
- Is CVE-2026-42048 exploitable, and should I be worried? Whether CVE-2026-42048 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-42048 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-42048? Upgrade
langflowto 1.9.0 or later.