Full Report
A high-severity unpatched security flaw in Langflow, an open-source low-code platform to build artificial intelligence (AI) applications, has come under active exploitation in the wild, according to findings from VulnCheck. The vulnerability in question is CVE-2026-5027 (CVSS score: 8.8), a case of path traversal that could allow an attacker to write files to arbitrary locations. "The 'POST /
Analysis Summary
# Vulnerability: Unpatched Path Traversal in Langflow Leading to RCE
## CVE Details
- **CVE ID:** CVE-2026-5027
- **CVSS Score:** 8.8 (High)
- **CWE:** CWE-22 (Improper Limitation of a Pathname to a Restricted Directory / Path Traversal)
## Affected Systems
- **Products:** Langflow (Open-source low-code AI application builder)
- **Versions:** Current versions as of June 2026 (Unpatched at time of report)
- **Configurations:** Systems where unauthenticated auto-login is enabled (default setting) and the instance is publicly exposed.
## Vulnerability Description
A path traversal flaw exists in the `POST /api/v2/files` endpoint of Langflow. The application fails to properly sanitize the `filename` parameter within the multipart form data. This allows an attacker to use traversal sequences (e.g., `../`) to escape the intended directory and write files to arbitrary locations on the host filesystem. In a security context, this can be leveraged to achieve Remote Code Execution (RCE).
## Exploitation
- **Status:** Exploited in the wild; active weaponization observed by VulnCheck.
- **Complexity:** Low (Single unauthenticated request can be sufficient).
- **Attack Vector:** Network (Remote)
## Impact
- **Confidentiality:** High (Potential for full system access)
- **Integrity:** High (Arbitrary file write capabilities)
- **Availability:** High (Potential for system disruption or total compromise)
## Remediation
### Patches
- **Status:** Unpatched. As of the report date, no official patch has been released by the project maintainers despite multiple disclosure attempts.
### Workarounds
- **Disable Auto-Login:** Modify the Langflow configuration to disable unauthenticated auto-login to prevent unauthorized access to the `/api/v2/files` endpoint.
- **Network Access Control:** Restrict access to Langflow instances using firewalls, VPNs, or IP allowlists to prevent exposure to the public internet.
- **File System Permissions:** Ensure the Langflow process runs with the least privilege possible to limit the impact of an arbitrary file write.
## Detection
- **Indicators of Compromise:**
- Presence of unexpected test files or web shells in application directories.
- Log entries showing `POST` requests to `/api/v2/files` containing `../` sequences in the `filename` parameter.
- **Detection methods and tools:**
- Monitor web server and application logs for path traversal patterns.
- Use external scanning tools (e.g., Censys) to identify if your Langflow instance is publicly reachable.
## References
- **NVD Detail:** hxxps[://]nvd[.]nist[.]gov/vuln/detail/CVE-2026-5027
- **Tenable Research Advisory:** hxxps[://]www[.]tenable[.]com/security/research/tra-2026-26
- **Source Article:** hxxps[://]thehackernews[.]com/2026/06/unpatched-langflow-flaw-cve-2026-5027[.]html