CVE-2026-5027 is a path traversal vulnerability in Langflow's 'POST /api/v2/files' endpoint that fails to sanitize the 'filename' parameter, allowing attackers to write files to arbitrary filesystem locations. Due to Langflow's default unauthenticated auto-login, attackers can access this endpoint without credentials, enabling remote code execution. Exploitation attempts have been confirmed, with attackers successfully dropping files on vulnerable systems. The vulnerability was disclosed publicly on March 27, 2026, by Tenable after failed disclosure attempts. The attack surface is broad, with thousands of internet-facing Langflow instances. No vendor advisory or patch information is currently available.

Successful exploitation allows unauthenticated remote attackers to write arbitrary files on the system, leading to remote code execution. This can compromise the affected system entirely, enabling attackers to execute arbitrary commands or payloads. The vulnerability affects internet-accessible Langflow instances, increasing the risk of widespread exploitation. Observed exploitation attempts confirm active threat activity targeting this flaw.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict access to Langflow instances from untrusted networks, disable or restrict the vulnerable endpoint if possible, and monitor for suspicious activity related to file uploads. Follow updates from Langflow and security advisories for patch releases.