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Atomicorp WAF Research Note: CVE-2026-9138

Langflow is vulnerable to arbitrary file write and arbitrary file deletion due to unvalidated paths in file-processing c

CVE Details

Status: Attack Blocked by Atomicorp
  • Already protected by existing Atomicorp WAF rules
  • Protection status: Understanding Atomicorp WAF Protection Status
  • CVE: CVE-2026-9138
  • Name: Langflow is vulnerable to arbitrary file write and arbitrary file deletion due to unvalidated paths in file-processing c
  • Severity: Medium
  • CVSS: 6.5 (v3.1) (Medium)
  • CVSS version: 3.1
  • CVSS source: ibm CNA
  • CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
    • Attack vector: Network
    • Attack complexity: Low
    • Privileges required: Low
    • User interaction: None
    • Scope: Unchanged
    • Confidentiality impact: None
    • Integrity impact: High
    • Availability impact: None
  • CWE: CWE-22 — Improper Limitation of a Pathname to a Restricted Directory (‘Path Traversal’)
  • Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-126 , CAPEC-64 , CAPEC-76 , CAPEC-78 , CAPEC-79
  • Vendor: langflow
  • Vulnerable product: langflow
  • CVE published: 2026-09-04
  • CVE last modified: 2026-09-10
  • Affected versions (NVD configurations):
    • langflow: >= 1.0.0, < 1.11.3
  • EPSS: 0.0030; 22.0th percentile (FIRST )
  • Latest Update: 2026-09-06
  • Selected Rule IDs observed: 340007 , 344360 , 390709
  • Matching rules: 3; rules with blocking actions: 3
  • Would-block Rule IDs: 340007 , 344360 , 390709
  • Request surfaces inspected: JSON request data, Request argument names, Request arguments, Request cookies, Request filename, SOAP request data, XML request data
Technical CPE data

This section lists vulnerable CPE matches retained from the NVD configurations. It supplements the readable affected-product information above.

  • cpe:2.3:a:langflow:langflow:*:*:*:*:*:*:*:*
    • Version start (inclusive): 1.0.0
    • Version end (exclusive): 1.11.3
    • NVD match criteria ID: E7183EAA-D662-465F-8176-7CCC96E6E470

Vulnerability Description

IBM Langflow OSS 1.0.0 through 1.11.2 Langflow could allow an authenticated attacker to write arbitrary files to the server due to improper input validation in the SaveToFileComponent. The application constructs local file paths using attacker‑controlled input without sufficient sanitization when handling requests to the /api/v1/run/{flow_id} endpoint. An attacker with low‑privileged authenticated access (such as a valid API key or user session) can supply crafted path values, including absolute paths or path traversal sequences, allowing arbitrary file writes to locations writable by the Langflow process. Successful exploitation may lead to unauthorized file creation or modification, potentially resulting in further compromise depending on the deployment environment.

  1. Maintain the observed Atomicorp protections. Keep your Atomicorp commercial rules current and confirm that the selected observed rules (340007 , 344360 , 390709 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

  2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

  3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

Test or Research Source

  • Source: Atomicorp AI Research Framework
  • Tags: cve, derived, traversal, waf-probe

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

  • Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
  • Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
  • Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
  • Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
  • Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ .