CVE-2026-42048: Langflow Knowledge Bases API is Vulnerable to Path Traversal

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.6%, percentile 48: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 48% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes langflow (PyPI) <= 1.8.4, fixed in 1.9.0. Check your lockfile, including transitive dependencies.

What it is

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.0, Langflow is vulnerable to Path Traversal in the Knowledge Bases API (DELETE /api/v1/knowledgebases). 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. This vulnerability is fixed in 1.9.0.

From the GitHub advisory

Summary Langflow is vulnerable to Path Traversal in the Knowledge Bases API (DELETE /api/v1/knowledgebases). 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 deleteknowledgebasesbulk function within src/backend/base/langflow/api/v1/knowledgebases.py.

This function constructs file paths directly from the user-supplied kbnames parameter. While other knowledge base endpoints safely route through standard path resolution (e.g., resolvekbpath()), 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 kbnames parameter: ../victimuser/kbname

Because the path is passed directly to shutil.rmtree() without containment checks, this payload deletes directories outside the intended scope.

Weakness type: CWE-22.

Product: langflow (PyPI) · Assigned by: GitHub_M · Published: 2026-05-12

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable no, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.60% probability of exploitation activity in the next 30 days; percentile 48.

Timeline

• 2026-05-05 — GitHub-reviewed advisory GHSA-9whx-c884-c68q published (critical)
• 2026-05-12 — CVE record published by GitHub_M
• 2026-05-13 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-9whx-c884-c68q github.com
2. CVE.org record CVE-2026-42048 cve.org
3. NVD entry CVE-2026-42048 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com

Critical PyPI advisories · Today’s Security Digest